Add workflow for automatically uploading config files to releases (#524)

This PR adds a workflow for automatically uploading config files to
releases. This prevents the maintainers forgetting uploading the files
and thus breaking the install guide.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Automated distribution of configuration files is now enabled for all
releases.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/upload-config-files-to-release

@@ -0,0 +1,20 @@
+name: Upload config files to release
+
+on:
+  release:
+    types: [published]
+
+permissions:
+  contents: write
+
+jobs:
+  release-assets:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - name: Upload files to GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          files: |
+            docker-compose.yaml
+            config.example.toml