add eslint

.eslintrc.js

@@ -0,0 +1,39 @@
+module.exports = {
+    "env": {
+        "commonjs": true,
+        "es2021": true,
+        "node": true
+    },
+    "extends": "eslint:recommended",
+    "parser": "babel-eslint",
+    "parserOptions": {
+        "ecmaVersion": 12
+    },
+    "rules": {
+        "indent": [
+            "error",
+            4
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "quotes": [
+            "error",
+            "double"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ],
+        "no-empty": [
+            "error",
+            { "allowEmptyCatch": true }
+        ],
+        "no-unused-vars": "warn",
+        "no-redeclare": "warn",
+        "no-constant-condition": "warn",
+        "no-useless-escape": "warn",
+        "no-case-declarations": "warn",
+    }
+};

.gitignore

@@ -1,3 +1,3 @@
 node_modules
 .vscode
-data
+data