ci: enforce semantic PRs

+name: "Semantic PRs"
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - synchronize
+
+jobs:
+  main:
+    name: Validate PR title
+    runs-on: ubuntu-latest
+    steps:
+      - uses: amannn/action-semantic-pull-request@v4
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}