Add linter actions

Author: xaviermarchegay

.github/workflows/super-linter.yml

@@ -0,0 +1,19 @@
+# It checks the syntax of the PHP code (using PHP-CS-Fixer)
+name: "Linter: Code Syntax"
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+jobs:
+    php-cs-fixer:
+        name: PHP-CS-Fixer
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v2
+            # see https://github.com/OskarStark/php-cs-fixer-ga
+            - name: PHP-CS-Fixer
+              uses: docker://oskarstark/php-cs-fixer-ga
+              with:
+                  args: --diff --dry-run