docs: added writing changeset docs

.changeset/README.md

@@ -39,9 +39,12 @@ A typical changeset file looks like this:
 '@spectrum-web-components/theme': patch
 ---
 
-Added new variant to button component and fixed theme compatibility issues
+-   **Added**: Added new variant `tertiary` to `<sp-button>` component [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+-   **Fixed**: Fixed `<sp-theme>` theme compatibility issues [#10000](https://github.com/adobe/spectrum-web-components/pull/10000)
 ```
 
+For our guidelines on writing changesets, see [our writing changesets guide](https://opensource.adobe.com/spectrum-web-components/guides/writing-changesets/).
+
 ## Common Questions
 
 We have a quick list of common questions to get you started engaging with this project in

README.md

@@ -103,7 +103,7 @@ The project will be linted on a pre-commit hook, but you can also run the lint s
 
 ### Dependency linting
 
-There are downstream issues that can arise from multiple packages in this mono-repo using dependencies with mismatched version strings. By default, changesets will bump version numbers of internal dependencies when the various packages are published and the depended version is pointing to the latest release, which can help to mitigate this issue. Running `yarn lint:versions` will check that all version strings for each dependency match across the repo.
+There are downstream issues that can arise from multiple packages in this mono-repo using dependencies with mismatched version strings. By default, [changesets](https://opensource.adobe.com/spectrum-web-components/guides/writing-changesets/) will bump version numbers of internal dependencies when the various packages are published and the depended version is pointing to the latest release, which can help to mitigate this issue. Running `yarn lint:versions` will check that all version strings for each dependency match across the repo.
 
 `yarn list:versions --fix` will modify the `package.json` files, updating all dependencies to the latest version available in the library — _a potentially dangerous operation_. If this is what you want to do when `yarn lint:versions` discovers mismatched versions, this step can greatly reduce the amount of work to achieve matching version numbers.
 

projects/documentation/content/guides/writing-changesets.md

@@ -0,0 +1,140 @@
+---
+layout: guide.njk
+title: 'Writing Changesets'
+displayName: Writing Changesets
+slug: writing-changesets
+---
+
+# What are changesets?
+
+Each changeset represents changes that have enough significance to warrant a new version. A changelog represents a single release. A changelog may contain several changesets.
+
+There are three levels of releases that a changeset can describe, which are described by semantic versioning:
+
+-   **Patch** (1.0.0 → 1.0.1): Bug fixes and non-breaking changes
+-   **Minor** (1.0.0 → 1.1.0): New features, backwards-compatible
+-   **Major** (1.0.0 → 2.0.0): Breaking changes requiring user update
+
+Each change should be categorized under one of these types:
+
+-   **Added**: New features or capabilities
+-   **Changed**: Changes in existing functionality
+-   **Deprecated**: Soon-to-be removed features
+-   **Removed**: Features that have been removed
+-   **Fixed**: Bug fixes
+
+## Writing changesets
+
+Changesets are different from commit messages. **Commit messages** are used to document the changes for _contributors_. **Changesets** are used to communicate the changes to the _consumers_ of the design system.
+
+### Be specific and component-focused
+
+Reference components by their tag names, include links to the PR, and be specific about changes, including:
+
+-   What changed
+-   Why it changed
+-   How users should update their code (if applicable)
+
+Use package names and categories for better readability. Make content easily linkable for reference.
+
+#### ❌ Bad: not specific
+
+```md
+---
+'@spectrum-web-components/alert': minor
+---
+
+-   Changed alert styles
+```
+
+#### ✅ Good: very specific
+
+```md
+---
+'@spectrum-web-components/alert': minor
+---
+
+-   **Fixed**: Updated `<sp-alert>` default styles for better contrast [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+### Document breaking changes
+
+Clearly mark and explain breaking changes with migration guidance. List each change on its own line.
+
+#### ❌ Bad: doesn't list breaking changes
+
+```md
+---
+'@spectrum-web-components/textfield': major
+---
+
+-   Changed how `<sp-textfield>` labels and placeholders work [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+#### ✅ Good: lists breaking changes
+
+```md
+---
+'@spectrum-web-components/textfield': major
+---
+
+-   **Deprecated**: Deprecated `label` attribute, which confused label with placeholder text. [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+-   **Added**: Added `hidden-label` attribute, for use with assistive technologies. (Before: `<sp-textfield label="Full Name"></sp-textfield>` / After: `<sp-textfield hidden-label="Full Name"></sp-textfield>`)
+-   **Added**: Added `placeholder` attribute, for placeholder text. (Before: `<sp-textfield label="john.smith@example.com"></sp-textfield>` / After: `<sp-textfield placeholder="john.smith@example.com"></sp-textfield>`)
+```
+
+### Focus on user impact
+
+Describe changes from the user's perspective, not implementation details.
+
+#### ❌ Bad: not user-focused
+
+```md
+---
+'@spectrum-web-components/overlay': patch
+---
+
+-   Replace native `showModal()` for performance optimization [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+#### ✅ Good: user-focused
+
+```md
+---
+'@spectrum-web-components/overlay': patch
+---
+
+-   **Fixed**: Improved `<sp-overlay>` performance in Chromium-based browsers. [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+### Use past tense
+
+Write changes in past tense to describe what has been modified.
+
+#### ❌ Bad: uses present tense
+
+```md
+---
+'@spectrum-web-components/button': minor
+---
+
+-   **Fixed**: Resolves `<sp-button>` accessibility [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+-   **Added**: Adds new variant `tertiary` [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+#### ✅ Good: usespast tense
+
+```md
+---
+'@spectrum-web-components/button': minor
+---
+
+-   **Fixed**: Resolved `<sp-button>` accessibility [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+-   **Added**: Added new variant `tertiary` [#9999](https://github.com/adobe/spectrum-web-components/pull/9999)
+```
+
+## Additional Resources
+
+-   [Changesets Documentation](https://github.com/changesets/changesets)
+-   [Common Questions](https://github.com/changesets/changesets/blob/main/docs/common-questions.md)
+-   [Detailed Release Process](https://github.com/changesets/changesets/blob/main/docs/detailed-explanation.md)