ci: add release-please workflow

Automate version bumps and changelog generation using release-please-action v4
with the simple release type. Uses the default GITHUB_TOKEN since release
commits contain no source changes and do not need to re-trigger CI.

Author: konokenj

.github/workflows/release-please.yml

@@ -0,0 +1,18 @@
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: write
+  pull-requests: write
+
+name: release-please
+
+jobs:
+  release-please:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: googleapis/release-please-action@v4
+        with:
+          release-type: simple