Add PHP CS Fixer and run it in CI

.github/workflows/php.yml

@@ -0,0 +1,19 @@
+on: [push, pull_request]
+name: PHP
+jobs:
+  php-cs-fixer:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 7.4
+
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Composer Install
+        run: composer install --ansi --prefer-dist --no-interaction --no-progress
+
+      - name: Run php-cs-fixer
+        run: ./vendor/bin/php-cs-fixer fix .  --dry-run --diff

.gitignore

@@ -1,2 +1,3 @@
 vendor/
-docs/
+docs/
+.php-cs-fixer.cache

composer.json

@@ -17,5 +17,8 @@
         "knplabs/github-api": "^2.12",
         "php-http/guzzle6-adapter": "^1.1",
         "nikic/php-parser": "^4.5"
+    },
+    "require-dev": {
+        "friendsofphp/php-cs-fixer": "^3.9"
     }
 }