Setup rector in CI

.github/workflows/rector.yaml

@@ -0,0 +1,35 @@
+# github action that checks code with Rector
+name: Rector
+
+on:
+    pull_request: null
+
+jobs:
+    rector:
+        runs-on: ubuntu-latest
+        if: github.event.pull_request.head.repo.full_name == 'mongodb/mongo-php-library'
+        steps:
+            -
+                if: github.event.pull_request.head.repo.full_name == github.repository
+                uses: actions/checkout@v3
+                with:
+                    # Must be used to trigger workflow after push
+                    token: ${{ secrets.ACCESS_TOKEN }}
+
+            -
+                uses: shivammathur/setup-php@v2
+                with:
+                    php-version: 8.1
+                    coverage: none
+
+            -   uses: "ramsey/composer-install@v2"
+
+            -   run: vendor/bin/rector --ansi
+
+            -
+                # commit only to core contributors who have repository access
+                uses: stefanzweifel/git-auto-commit-action@v4
+                with:
+                    commit_message: '[rector] Rector fixes'
+                    commit_author: 'GitHub Action <[email protected]>'
+                    commit_user_email: '[email protected]'