Restore dev dependencies

Author: Brylie Christopher Oxley

composer.json

@@ -13,6 +13,13 @@
       "email": "brylie@creativecommons.org"
     }
   ],
+  "require-dev": {
+    "php-parallel-lint/php-parallel-lint": "^1.1",
+    "phpcompatibility/php-compatibility": "^9.1",
+    "squizlabs/php_codesniffer": "3.*",
+    "wp-coding-standards/wpcs": "^2.0",
+    "dealerdirect/phpcodesniffer-composer-installer": "^0.7.1"
+  },
   "scripts": {
     "compat": "phpcs -p --standard=PHPCompatibility --runtime-set testVersion 7.0 -n . --extensions=php --cache",
     "fix": "phpcbf --standard=WordPress . --extensions=php --ignore=vendor",