Add test files for .fhirpath, .fsh, and .feature file types (#29)

## Plan: Add Example Test Files for File Types

- [x] Create `test-fhirpath.fhirpath` file with example FHIRPath content
- [x] Create `test-fsh.fsh` file with example FHIR Shorthand content  
- [x] Create `test-feature.feature` file with example Gherkin BDD test
content
- [x] Verify files are created correctly and follow the pattern of
existing test files
- [x] Run validation to ensure no issues introduced (all tests passed)
- [x] Simplify test-feature.feature to only include Scenario Outline
with background
- [x] Simplify test-fhirpath.fhirpath by removing observations and age
calculation examples

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<details>

<summary>Original prompt</summary>

> On file-types-test, Can we add the following example test files in
`workspace-wiki/example/file-types-test/` for the following please:
> ```
> .fhirpath
> .fsh
> .feature (Gherkin feature BDD test file)
> ```


</details>



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Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: AlexJSully <[email protected]>

Author: Copilot

example/file-types-test/test-feature.feature

@@ -0,0 +1,26 @@
+# test-feature.feature
+# This is a Gherkin feature file for BDD testing in Workspace Wiki
+
+Feature: Workspace Wiki File Type Support
+  As a developer
+  I want to test different file types
+  So that the Workspace Wiki extension can handle various documentation formats
+
+  Background:
+    Given the Workspace Wiki extension is installed
+    And the workspace contains the file-types-test directory
+
+  Scenario Outline: Handle different file extensions
+    Given I have a file with extension "<extension>"
+    When the Workspace Wiki scans the workspace
+    Then the file should be "<visibility>" in the tree view
+
+    Examples:
+      | extension | visibility |
+      | .md       | visible    |
+      | .txt      | visible    |
+      | .html     | visible    |
+      | .js       | hidden     |
+      | .py       | hidden     |
+      | .fhirpath | hidden     |
+      | .fsh      | hidden     |

example/file-types-test/test-fhirpath.fhirpath

@@ -0,0 +1,14 @@
+// test-fhirpath.fhirpath
+// This is a FHIRPath expression file for testing Workspace Wiki file type support
+
+// FHIRPath is a navigation and extraction language for FHIR resources
+// Used in healthcare interoperability to query and filter FHIR data
+
+// Example: Get patient's first name
+Patient.name.first().given.first()
+
+// Example: Check if patient is active
+Patient.active = true
+
+// Example: Filter medications by status
+MedicationRequest.where(status = 'active')

example/file-types-test/test-fsh.fsh

@@ -0,0 +1,32 @@
+// test-fsh.fsh
+// This is a FHIR Shorthand (FSH) file for testing Workspace Wiki file type support
+
+// FHIR Shorthand is a domain-specific language for defining FHIR resources
+// Used in healthcare interoperability to create FHIR Implementation Guides
+
+Profile: ExamplePatientProfile
+Parent: Patient
+Id: example-patient
+Title: "Example Patient Profile"
+Description: "An example patient profile for testing purposes"
+* name 1..* MS
+* name.given 1..* MS
+* name.family 1..1 MS
+* birthDate 1..1 MS
+* active 1..1 MS
+
+Instance: ExamplePatientInstance
+InstanceOf: ExamplePatientProfile
+Usage: #example
+Title: "Example Patient Instance"
+Description: "An example patient instance for testing"
+* name.given = "John"
+* name.family = "Doe"
+* birthDate = "1980-01-01"
+* active = true
+
+ValueSet: ExampleValueSet
+Id: example-value-set
+Title: "Example Value Set"
+Description: "An example value set for testing"
+* include codes from system http://example.org/fhir/CodeSystem/example-codes