TASK: Provide phpcs integration for CGL

Use common accepted PSR2 for CGL checks.

composer.json

@@ -12,9 +12,16 @@
     },
     "require": {
         "php": ">=7.0.0 <=7.2.99",
-        "typo3/cms-core": ">=8.7.0,<8.9.99"
+        "typo3/cms-core": "^8.7.0",
+        "typo3/cms-form": "^8.7.0"
+    },
+    "require-dev": {
+        "squizlabs/php_codesniffer": "^3.2.0"
     },
     "scripts": {
+        "lint": [
+            "./vendor/bin/phpcs"
+        ],
         "post-install-cmd": [
             "npm install"
         ]

phpcs.xml.dist

@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<ruleset name="cgl">
+    <description>The coding standard for this extension.</description>
+
+    <file>./Classes/</file>
+
+    <!-- Set default settings -->
+    <arg value="sp"/>
+    <arg name="colors"/>
+    <arg name="encoding" value="utf-8" />
+    <arg name="extensions" value="php" />
+
+    <rule ref="PSR2">
+        <!-- As it does not work with new array syntax. -->
+        <exclude name="Squiz.Arrays.ArrayBracketSpacing.SpaceBeforeBracket" />
+    </rule>
+</ruleset>