Add tools for js code formatting and linting

Due to eslint couldn't correctly resolve the context for the variables,
two eslint rules are disabled for now.

src/webui/www/.eslintrc.json

@@ -0,0 +1,14 @@
+{
+    "env": {
+        "browser": true,
+        "es2020": true
+    },
+    "extends": "eslint:recommended",
+    "plugins": [
+        "html"
+    ],
+    "rules": {
+        "no-undef": "off",
+        "no-unused-vars": "off"
+    }
+}

src/webui/www/.jsbeautifyrc

@@ -11,7 +11,7 @@
     "space_in_empty_paren": false,
     "jslint_happy": false,
     "space_after_anon_function": false,
-    "brace_style": "end-expand",
+    "brace_style": "end-expand,preserve-inline",
     "unindent_chained_methods": false,
     "break_chained_methods": false,
     "keep_array_indentation": false,

src/webui/www/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "webui",
+  "description": "qBittorrent WebUI",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/qbittorrent/qBittorrent.git"
+  },
+  "scripts": {
+    "format": "js-beautify private/*.html private/scripts/*.js private/views/*.html public/*.html public/scripts/*.js",
+    "lint": "eslint private/*.html private/scripts/*.js private/views/*.html public/*.html public/scripts/*.js"
+  },
+  "devDependencies": {
+    "eslint": "*",
+    "eslint-plugin-html": "*",
+    "js-beautify": "*"
+  }
+}