Replace Prettier with eslint

.eslintignore

@@ -0,0 +1,7 @@
+# Build
+/vendor/
+/coverage/
+# Language files written automatically by TranslateWiki
+/i18n/**/*.json
+!/i18n/**/en.json
+!/i18n/**/qqq.json

.eslintrc.json

@@ -0,0 +1,7 @@
+{
+	"root": true,
+	"extends": [
+		"wikimedia/server",
+		"wikimedia/mediawiki"
+	]
+}

Gruntfile.js

@@ -0,0 +1,26 @@
+'use strict';
+module.exports = function ( grunt ) {
+	const conf = grunt.file.readJSON( 'extension.json' );
+	grunt.loadNpmTasks( 'grunt-banana-checker' );
+	grunt.loadNpmTasks( 'grunt-eslint' );
+	grunt.loadNpmTasks( 'grunt-stylelint' );
+	grunt.initConfig( {
+		eslint: {
+			options: {
+				cache: true,
+				fix: grunt.option( 'fix' )
+			},
+			all: '.'
+		},
+		stylelint: {
+			all: [
+				'**/*.{css,less}',
+				'!node_modules/**',
+				'!vendor/**'
+			]
+		},
+		banana: conf.MessagesDirs
+	} );
+	grunt.registerTask( 'test', [ 'eslint', 'stylelint', 'banana' ] );
+	grunt.registerTask( 'default', 'test' );
+};

package.json

@@ -3,24 +3,19 @@
   "description": "Let users handle sanctions.",
   "private": true,
   "scripts": {
-    "test": "npm -s run lint",
-    "lint": "npm -s run lint:prettier && npm -s run lint:i18n",
-    "lint:prettier": "prettier '**/*.{js,json,css,less,md,yml}' --check",
+    "test": "grunt test",
     "lint:i18n": "banana-checker --requireLowerCase=0 i18n/",
-    "fix": "prettier '**/*.{js,json,css,less,md,yml}' --write",
     "minify-svg": "svgo --config=.svgo.config.js -q -r -f modules/visualeditor/ui/images/",
     "selenium-daily": "npm run selenium-test",
     "selenium-test": "wdio tests/selenium/wdio.conf.js"
   },
   "devDependencies": {
-    "@prettier/plugin-xml": "^2.2.0",
     "@wdio/cli": "^7.29.1",
     "@wdio/dot-reporter": "^7.25.1",
     "@wdio/junit-reporter": "^7.26.0",
     "@wdio/local-runner": "^7.20.9",
     "@wdio/mocha-framework": "^7.24.1",
     "grunt-banana-checker": "^0.10.0",
-    "prettier": "^2.8.1",
     "svgo": "^2.3.1",
     "wdio-mediawiki": "^2.2.0"
   }