feat: add TypeScript rules (#230)

* feat: add TypeScript rules

* feat: install eslint-import-resolver-typescript to support .modified

#230 (comment)

* lint .tsx files

Co-authored-by: Matt Kane <matt.kane@netlify.com>

Co-authored-by: Netlify Team Account 1 <netlify-team-account-1@users.noreply.github.com>
Co-authored-by: Netlify Team Account 1 <90322326+netlify-team-account-1@users.noreply.github.com>
Co-authored-by: Matt Kane <matt.kane@netlify.com>

Author: 3 people

.eslintrc.js

@@ -178,6 +178,12 @@ module.exports = {
     'node/no-mixed-requires': 2,
     // Using path.join() is often not needed when using only core Node.js APIs
     'node/no-path-concat': 0,
+    'node/no-unsupported-features/es-syntax': [
+      'error',
+      {
+        ignores: ['modules'],
+      },
+    ],
     // Browser globals should not use `require()`. Non-browser globals should
     'node/prefer-global/console': 2,
     'node/prefer-global/buffer': [2, 'never'],
@@ -299,6 +305,15 @@ module.exports = {
         'import/no-extraneous-dependencies': 0,
       },
     },
+    // TypeScript-specific settings.
+    {
+      files: ['*.ts', '*.tsx'],
+      extends: [
+        'plugin:@typescript-eslint/eslint-recommended',
+        'plugin:@typescript-eslint/recommended',
+        'plugin:import/typescript',
+      ],
+    },
     {
       // ES modules
       files: ['*.mjs'],
@@ -311,6 +326,20 @@ module.exports = {
     },
   ],
   settings: {
+    'import/parsers': {
+      '@typescript-eslint/parser': ['.ts', '.tsx'],
+    },
+    'import/resolver': {
+      node: {
+        extensions: ['.js', '.jsx', '.d.ts', '.ts', '.tsx'],
+      },
+      typescript: {
+        alwaysTryTypes: true,
+      },
+    },
+    node: {
+      tryExtensions: ['.js', '.ts', '.d.ts'],
+    },
     react: {
       version: '16.13.1',
     },