feat(changelog): scaffold changelog workflow

This uses all the default configuration. Probably needs some refining
but I'm going to use this to test that the trigger works correctly.

.github/workflows/changelog.yml

@@ -0,0 +1,14 @@
+name: changelog
+
+on:
+  workflow_call:
+
+jobs:
+  changelog:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: TriPSs/conventional-changelog-action@v5
+        with:
+          github-token: ${{ secrets.github_token }}