refactor: backend to es6-style syntax

chore: introduce eslint (resolve #53)

.eslintrc.json

@@ -0,0 +1,74 @@
+{
+    "env": {
+        "browser": true,
+        "commonjs": true,
+        "es2021": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+        "ecmaVersion": 13
+    },
+    "rules": {
+        "indent": [
+            "error",
+            4
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "quotes": [
+            "error",
+            "single"
+        ],
+        "semi": [
+            "error",
+            "never"
+        ],
+        "prefer-arrow-callback": [
+            "error"
+        ],
+        "prefer-template": [
+            "error"
+        ],
+        "no-useless-concat": [
+            "error"
+        ],
+        "no-var": [
+            "error"
+        ],
+        "prefer-const": [
+            "error"
+        ],
+        "sort-imports": [
+            "error"
+        ],
+        "no-extra-semi": [
+            "error"
+        ],
+        "array-bracket-spacing": [
+            "error"
+        ],
+        "arrow-spacing": [
+            "error"
+        ],
+        "comma-spacing": [
+            "error"
+        ],
+        "eol-last": [
+            "error",
+            "never"
+        ],
+        "indent": [
+            "error",
+            4
+        ],
+        "template-curly-spacing": [
+            "error",
+            "never"
+        ],
+        "no-prototype-builtins": [
+            "off"
+        ]
+    }
+}

README.md

@@ -116,8 +116,8 @@ You can integrate Anchr with [ShareX](https://github.com/ShareX/ShareX) on Windo
     * [`sharex-shortlinks.json`](scripts/sharex-shortlinks.json)
 1. Import both files as custom uploaders in ShareX
 
-## 🧩 Project State
-The project's origins lie in 2014, back when the [MEAN stack](https://www.mongodb.com/mean-stack) was the sh*t. It was the author's first real web project and a great opportunity to learn. The project is maintained ever since, however, considered mostly feature-complete. Dependencies are updated occasionally. Because the project started quite a couple of years ago, it is still based on old-fashioned JavaScript ES5 syntax, alongside vintage tools like [Grunt](https://gruntjs.com/) and [Bower](https://bower.io/). Certainly, this is not state-of-the-art in web dev anymore. However, to keep consistency with existing code, the original code style should still be followed in new contributions. Please don't use `const` and `let`, template strings, arrow functions, `async / await` etc.
+## 🧩 Project History
+The project's origins lie in 2014, back when the [MEAN stack](https://www.mongodb.com/mean-stack) was the sh*t. It was the author's first real web project and a great opportunity to learn. The project is maintained ever since, however, considered mostly feature-complete. Dependencies are updated occasionally. Because the project started quite a couple of years ago, some parts are still based on old-fashioned JavaScript ES5 syntax, alongside vintage tools like [Grunt](https://gruntjs.com/) and [Bower](https://bower.io/). Certainly, this is not state-of-the-art in web dev anymore. However, to keep consistency with existing code, the original code style should still be followed in new contributions. **Update:** Just [recently](https://github.com/muety/anchr/issues/54), all backend-side code was refactored to modern JavaScript syntax to ease development. 
 
 ## 📓 License
 GNU General Public License v3 (GPL-3) @ [Ferdinand Mütsch](https://muetsch.io)