Improve vite development server config

[AlemTuzlak]

There are a few things these PR aims to achieve:

1. Current setup runs the vite custom server in middleware mode but because we do not specify the appType it's set to SPA which runs HTML transforming middleware which we don't want to do as the "custom" property is the correct type to use (reference here: https://vite.dev/config/server-options.html#server-middlewaremode)

Test Plan

Should work the same as before:

• local dev server starts normally and everything works

Checklist

• Tests updated
• Docs updated

Screenshots

[Copilot]

Pull Request Overview

This PR improves the Vite development server configuration by adjusting middleware settings and port assignment logic, ensuring the custom server runs with the correct appType and handles port collisions as expected. Key changes include:

• Refining the server startup logic to determine and set the appropriate port.
• Configuring Vite with the custom appType to bypass unnecessary HTML transformation.
• Updating the react-router-devtools dependency and adding a request filter in mocks.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tests/mocks/index.ts	Adds a filter to ignore custom requests from react-router-devtools.
server/index.ts	Updates Vite dev server configuration with port determination and appType.
package.json	Updates the react-router-devtools dependency version.

[kentcdodds]

Thanks!