Added TypeScript for frontend

Added type definitions for components, functions, data
Added guards for network responses
fixes #8

front/.eslintrc.cjs

@@ -1,16 +1,27 @@
+/* eslint-env node */
+
 module.exports = {
+  root: true,
   env: { browser: true, es2020: true },
   extends: [
     'eslint:recommended',
-    'plugin:react/recommended',
-    'plugin:react/jsx-runtime',
+    'plugin:@typescript-eslint/recommended',
+    'plugin:@typescript-eslint/recommended-requiring-type-checking',
     'plugin:react-hooks/recommended',
   ],
-  parserOptions: { ecmaVersion: 'latest', sourceType: 'module' },
-  settings: { react: { version: '18.2' } },
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+    project: true,
+    tsconfigRootDir: __dirname,
+  },
   plugins: ['react-refresh'],
   rules: {
-    'react-refresh/only-export-components': 'warn',
-    'react/prop-types': 'off'
+    'react-refresh/only-export-components': [
+      'warn',
+      { allowConstantExport: true },
+    ],
+    '@typescript-eslint/no-non-null-assertion': 'off',
   },
 }