chore: run PHPStan in CI

Author: martingold

.github/workflows/phpstan.yml

@@ -0,0 +1,28 @@
+# Update this by running
+# curl https://gist.githubusercontent.com/mpdude/ca93a185bcbf56eb7e341632ad4f8263/raw/fix-cs-php.yml > .github/workflows/fix-cs-php.yml
+
+on:
+  push:
+    branches: ['master']
+  pull_request:
+    branches: ['*']
+
+name: Coding Standards
+
+jobs:
+  phpstan:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@main
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.3
+
+      - name: Install Composer dependencies
+        run: composer install --no-progress --prefer-dist
+
+      - name: Run PHPStan
+        run: composer run phpstan