build: Creating workflow `commitlint.yml`.

The .github/workflows/commitlint.yml workflow is missing or needs an update to stay in
sync with the current standard for this workflow as defined in the
`.github` repo of the `openedx` GitHub org.

Author: arbrandes

.github/workflows/commitlint.yml

@@ -0,0 +1,10 @@
+# Run commitlint on the commit messages in a pull request.
+
+name: Lint Commit Messages
+
+on:
+  - pull_request
+
+jobs:
+  commitlint:
+    uses: openedx/.github/.github/workflows/commitlint.yml@master