Add Release Notes column to API reference versions table (#225)

The API reference landing page versions table had no link to per-version
changelog/release notes.

## Changes

- **`publish-documentation.yml`**: Added a "Release Notes" column to the
generated "Released Versions" table; each entry links to the
corresponding GitHub Release page (`releases/tag/v<version>`), which is
already auto-populated from `CHANGELOG.md` by the release workflow.

The generated table now looks like:

| Version | Guide | API Reference | Release Notes |
|---------|-------|---------------|---------------|
| v1.0 (latest) | Guide | API Reference | [Release
Notes](https://github.com/petesramek/polyline-algorithm-csharp/releases/tag/v1.0)
|

Author: Copilot

.github/workflows/publish-documentation.yml

@@ -151,15 +151,15 @@ jobs:
           {
             echo "## Released Versions"
             echo ""
-            echo "| Version | Guide | API Reference |"
-            echo "|---------|-------|---------------|"
+            echo "| Version | Guide | API Reference | Release Notes |"
+            echo "|---------|-------|---------------|---------------|"
             for ver in $(echo "${{ steps.discover-versions.outputs.versions }}" | tr ',' '\n' | sort -Vr); do
               if [ "$ver" = "$latest" ]; then
                 label="v${ver} (latest)"
               else
                 label="v${ver}"
               fi
-              echo "| ${label} | [Guide](${ver}/guide/getting-started.html) | [API Reference](${ver}/PolylineAlgorithm.html) |"
+              echo "| ${label} | [Guide](${ver}/guide/getting-started.html) | [API Reference](${ver}/PolylineAlgorithm.html) | [Release Notes](https://github.com/petesramek/polyline-algorithm-csharp/releases/tag/v${ver}) |"
             done
           } > /tmp/versions_section.md
           awk '/{versions_section}/{while((getline line < "/tmp/versions_section.md") > 0) print line; close("/tmp/versions_section.md"); next} {print}' \