Merge pull request heroku#924 from heroku/schneems/force-changelog

[changelog skip] Introduce change log check to all PRs

.github/workflows/check_changelog.yml

@@ -0,0 +1,12 @@
+name: Check Changelog
+
+on: [pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Check that CHANGELOG is touched
+      run: |
+        cat $GITHUB_EVENT_PATH | jq .pull_request.title |  grep -i '\[\(\(changelog skip\)\|\(ci skip\)\)\]' ||  git diff remotes/origin/${{ github.base_ref }} --name-only | grep CHANGELOG.md