docs(github-action): improve & update (#59)

* docs(github-action): update php to 8.1

* docs(github-actions): add composer install step

Author: SimJoSt

README.md

@@ -97,7 +97,10 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '8.0'
+          php-version: '8.1'
+
+      - name: Install dependencies
+        run: composer install
 
       - name: Deploy
         uses: deployphp/action@v1