ci: Add semantic PR title check (#979)

This adds a new workflow to check semantic PR titles to match the
[Conventional Commits spec](https://www.conventionalcommits.org/). This
will make it easier to browse commit history and enable automation in
the future.

---------

Signed-off-by: Yuan Tang <terrytangyuan@gmail.com>

.github/workflows/semantic-pr.yml

@@ -0,0 +1,21 @@
+name: Check semantic PR titles
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+
+permissions:
+  contents: read
+
+jobs:
+  title-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check PR Title's semantic conformance
+        uses: amannn/action-semantic-pull-request@v5
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}