add eslint & format code

Author: schl3ck

.eslintrc.json

@@ -0,0 +1,83 @@
+{
+  "env": {
+    "es6": true,
+    "node": true
+  },
+  "parserOptions": {
+    "sourceType": "script",
+    "ecmaVersion": 2021
+  },
+  "rules": {
+    "indent": [
+      "error",
+      2,
+      {
+        "SwitchCase": 1,
+        "CallExpression": {
+          "arguments": "off"
+        },
+        "ArrayExpression": 1,
+        "ignoreComments": true
+      }
+    ],
+    "max-len": [
+      "error",
+      {
+        "code": 80,
+        "ignoreComments": true,
+        "ignoreUrls": true,
+        "ignoreStrings": true,
+        "ignoreTemplateLiterals": true,
+        "ignoreRegExpLiterals": true
+      }
+    ],
+    "quotes": [
+      "error",
+      "double",
+      {
+        "avoidEscape": true
+      }
+    ],
+    "array-bracket-spacing": ["error", "never"],
+    "object-curly-spacing": ["error", "always"],
+    "space-in-parens": ["error", "never"],
+    "no-empty": ["off"],
+    "linebreak-style": ["off", "unix"],
+    "semi": ["error", "always"],
+    "no-unused-vars": "warn",
+    "space-before-function-paren": ["error", "never"],
+    "comma-dangle": [
+      "error",
+      {
+        "arrays": "always-multiline",
+        "objects": "always-multiline",
+        "imports": "always-multiline",
+        "exports": "always-multiline",
+        "functions": "always-multiline"
+      }
+    ],
+    "operator-linebreak": [
+      "error",
+      "before",
+      {
+        "overrides": {
+          "=": "after",
+          "*=": "after",
+          "**=": "after",
+          "/=": "after",
+          "%=": "after",
+          "+=": "after",
+          "-=": "after",
+          "<<=": "after",
+          ">>=": "after",
+          ">>>=": "after",
+          "&=": "after",
+          "^=": "after",
+          "|=": "after",
+          "&&=": "after",
+          "??=": "after"
+        }
+      }
+    ]
+  }
+}

.prettierrc.json

@@ -1,7 +1,12 @@
 {
-    "$schema": "http://json.schemastore.org/prettierrc",
-    "singleQuote": true,
-    "trailingComma": "all",
-    "tabWidth": 4,
-    "printWidth": 120
+  "printWidth": 80,
+  "tabWidth": 2,
+  "useTabs": false,
+  "semi": true,
+  "singleQuote": false,
+  "quoteProps": "as-needed",
+  "trailingComma": "es5",
+  "bracketSpacing": true,
+  "arrowParens": "always",
+  "endOfLine": "lf"
 }