ci: enforce PR titles to follow the conventional commit specification (#3204)

As per decision in #3083, we want to use the conventional commits in our repository. To make sure this actually happens, this patch adds a workflow that validates PR titles to follow this convention. Together with our mergify configuration, these PR titles end up being the commit message title when squash-merging a pull request.

Related: #3083
Related: libp2p/github-mgmt#93

Author: thomaseizinger

.github/dependabot.yml

@@ -5,9 +5,11 @@ updates:
     schedule:
       interval: "daily"
     open-pull-requests-limit: 9999
-
+    commit-message:
+      prefix: "deps"
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      # Check for updates to GitHub Actions every weekday
       interval: "daily"
+    commit-message:
+      prefix: "deps"

.github/workflows/ci.yml

@@ -267,3 +267,24 @@ jobs:
         run: |
           WORKSPACE_MEMBERS=$(cargo metadata --format-version=1 --no-deps | jq -c '.packages | .[] | select(.publish == null) | .name' | jq -s '.' | jq -c '.')
           echo "members=${WORKSPACE_MEMBERS}" >> $GITHUB_OUTPUT
+
+  validate_pr_title:
+    name: Validate PR title
+    runs-on: ubuntu-latest
+    if: ${{ github.event_name == 'pull_request' }}
+    steps:
+      - uses: amannn/action-semantic-pull-request@01d5fd8a8ebb9aafe902c40c53f0f4744f7381eb # v5.0.2
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          # Configure which types are allowed (newline delimited).
+          types: |
+            feat
+            fix
+            chore
+            docs
+            deps
+            test
+            ci
+            refactor
+          require_scope: false