Add phpcs as dev dependency, bump version

Author: fabianmichael

composer.json

@@ -4,7 +4,7 @@
 	"homepage": "https://github.com/fabianmichael/kirby-template-attributes",
 	"license": "MIT",
 	"type": "kirby-plugin",
-	"version": "2.0.0",
+	"version": "2.1.0",
 	"authors": [
 		{
 			"name": "Fabian Michael",
@@ -16,7 +16,8 @@
 		"phpunit/phpunit": "^9",
 		"phpmd/phpmd" : "@stable",
 		"vimeo/psalm": "^5.1",
-		"getkirby/cms": "^4.0.0"
+		"getkirby/cms": "^4.0.0",
+		"squizlabs/php_codesniffer": "^3.9"
 	},
 	"require": {
 		"getkirby/composer-installer": "^1.2"