Add linter

.eslintrc.json

@@ -0,0 +1,34 @@
+{
+    "env": {
+        "browser": true,
+        "es2021": true
+    },
+    "extends": ["plugin:react/recommended"],
+    "overrides": [],
+    "parserOptions": {
+        "ecmaVersion": "latest",
+        "ecmaFeatures": { "jsx": true },
+        "sourceType": "module"
+    },
+    "parser": "@babel/eslint-parser",
+    "plugins": ["react"],
+    "settings": {
+        "react": {
+            "version": "detect"
+        }
+    },
+    "rules": {
+        "eqeqeq": "error",
+        "no-unreachable": "error",
+        "no-duplicate-imports": "error",
+        "no-multiple-empty-lines": "warn",
+        "indent": ["warn", 4],
+        "quotes": ["warn", "double"],
+        "newline-before-return": "warn",
+        "padding-line-between-statements": [
+            "warn",
+            { "blankLine": "always", "prev": "*", "next": "export" }
+        ]
+    },
+    "ignorePatterns": ["node_modules", "build", "dist", "public"]
+}

.prettierrc.json

@@ -0,0 +1,6 @@
+{
+  "trailingComma": "es5",
+  "tabWidth": 4,
+  "semi": true,
+  "singleQuote": false
+}

babel.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+    presets: ["@babel/preset-typescript", "@babel/preset-env"],
+};