ci: lint PR titles according to conventional commits (#1615)

* CI: add validation for PR titles

This will help us to automate release notes in future

* Fix: try putting CI workflows in correct location

:cry:

* WIP: use `pull_request` to trigger CI for initial commit

.github/workflows/semantic-pr-title.yml

@@ -0,0 +1,18 @@
+name: "Lint PR"
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - synchronize
+  workflow_dispatch:
+
+jobs:
+  main:
+    name: Validate PR title
+    runs-on: ubuntu-latest
+    steps:
+      - uses: amannn/action-semantic-pull-request@v4
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}