add eslint and editorconfig

This commit adds a simple editorconfig generated via VSCode
and .eslintrc.json configuration created with 'npx eslint --init'.
The rules are react-specific typescript recommnedations with
the Airbnb style guide. Linting can be performed by running 'npm
run lint' or fix possible errors with 'npm run eslintfix'. These
commands are located in the pacakge.json 'scripts' configuration.
Place file extensions and directories to be ignored in .eslintignore.

.editorconfig

@@ -0,0 +1,12 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = false
+insert_final_newline = false

.eslintignore

@@ -0,0 +1,3 @@
+*.css
+*.svg
+*.png

.eslintrc.json

@@ -0,0 +1,42 @@
+{
+    "env": {
+        "browser": true,
+        "es2021": true
+    },
+    "extends": [
+        "plugin:@typescript-eslint/recommended",
+        "plugin:react/recommended",
+        "airbnb"
+    ],
+    "parser": "@typescript-eslint/parser",
+    "parserOptions": {
+        "ecmaFeatures": {
+            "jsx": true
+        },
+        "ecmaVersion": 12,
+        "sourceType": "module"
+    },
+    "plugins": [
+        "react",
+        "react-hooks",
+        "@typescript-eslint"
+    ],
+    "rules": {
+        "no-use-before-define": "off",
+        "@typescript-eslint/no-use-before-define": ["error"],
+        "react/jsx-filename-extension": [ "warn", {"extensions": [".tsx"]}],
+        "import/extensions": ["error","ignorePackages",{"ts": "never", "tsx": "never" }],
+        "@typescript-eslint/explicit-function-return-type": ["error",{"allowExpressions": true}],
+        "no-shadow": "off", "@typescript-eslint/no-shadow": ["error"],
+        "max-len": ["warn", { "code": 80 }],
+        "react-hooks/rules-of-hooks": "error",
+        "react-hooks/exhaustive-deps": "warn",
+        "import/prefer-default-export": "off",
+        "react/prop-types": "off"
+    },
+    "settings": {
+        "import/resolver": {
+        "typescript": {}
+        }
+    }
+}

package.json

@@ -22,13 +22,9 @@
     "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
-    "eject": "react-scripts eject"
-  },
-  "eslintConfig": {
-    "extends": [
-      "react-app",
-      "react-app/jest"
-    ]
+    "eject": "react-scripts eject",
+    "lint": "eslint src/*",
+    "eslintfix": "eslint src/* --fix"
   },
   "browserslist": {
     "production": [
@@ -43,6 +39,15 @@
     ]
   },
   "devDependencies": {
+    "@typescript-eslint/eslint-plugin": "^4.31.1",
+    "@typescript-eslint/parser": "^4.31.1",
+    "eslint": "^7.32.0",
+    "eslint-config-airbnb": "^18.2.1",
+    "eslint-import-resolver-typescript": "^2.5.0",
+    "eslint-plugin-import": "^2.24.2",
+    "eslint-plugin-jsx-a11y": "^6.4.1",
+    "eslint-plugin-react": "^7.25.2",
+    "eslint-plugin-react-hooks": "^4.2.0",
     "monero-javascript": "^0.5.5"
   }
 }