Add php compatibility check (#383)

Author: lens0021

.gitignore

@@ -1,6 +1,9 @@
-vendor/
 node_modules/
 .eslintcache
 tests/selenium/log
 # We use yarn instead of npm
 package-lock.json
+
+# composer dependencies
+/vendor/
+composer.lock

composer.json

@@ -6,7 +6,9 @@
     "mediawiki/mediawiki-phan-config": "0.12.0",
     "mediawiki/minus-x": "1.1.1",
     "php-parallel-lint/php-console-highlighter": "1.0.0",
-    "php-parallel-lint/php-parallel-lint": "1.3.2"
+    "php-parallel-lint/php-parallel-lint": "1.3.2",
+    "phpcompatibility/php-compatibility": "9.3.5",
+    "dealerdirect/phpcodesniffer-composer-installer": "0.7.2"
   },
   "scripts": {
     "fix": [
@@ -18,5 +20,10 @@
       "phpcs -p -s",
       "minus-x check ."
     ]
+  },
+  "config": {
+    "allow-plugins": {
+      "dealerdirect/phpcodesniffer-composer-installer": true
+    }
   }
 }