Add a GitHub CHANGELOG/News Check (#2057)

- Run grep to see commit has a line mentioning it to CHANGES.md
- Also add a label to disable this being required for PRs that don't need a change entry

.github/workflows/changelog.yml

@@ -0,0 +1,21 @@
+name: changelog
+
+on:
+  pull_request:
+    types: [opened, synchronize, labeled, unlabeled, reopened]
+
+jobs:
+  build:
+    name: Changelog Entry Check
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Grep CHANGES.md for PR number
+        if: contains(github.event.pull_request.labels.*.name, 'skip news') != true
+        run: |
+          grep -P "PR #${{ github.event.pull_request.number }}[^0-9]" CHANGES.md || \
+          (echo "Please add 'PR #${{ github.event.pull_request.number }}' change line to CHANGES.md" && \
+          exit 1)