Add auto changelog workflow

Borrowed from Dries tweet.

https://twitter.com/driesvints/status/1492241552508432391

.github/workflows/update-changelog.yml

@@ -0,0 +1,29 @@
+name: "Update Changelog"
+
+on:
+  release:
+    types: [released]
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.ref_name }}
+
+      - name: Update Changelog
+        uses: stefanzweifel/changelog-updater-action@v1
+        with:
+          latest-version: ${{ github.event.release.tag_name }}
+          release-notes: ${{ github.event.release.body }}
+          compare-url-target-revision: ${{ github.event.release.target_commitish }}
+
+      - name: Commit updated CHANGELOG
+        uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          branch: ${{ github.event.release.target_commitish }}
+          commit_message: Update CHANGELOG.md
+          file_pattern: CHANGELOG.md