Linting rules to make sure we use extensions

Author: ahocevar

.vscode/extensions.json

@@ -0,0 +1,3 @@
+{
+  "recommendations": ["Vue.volar", "dbaeumer.vscode-eslint"]
+}

eslint.config.js

@@ -1,19 +1,38 @@
 import js from '@eslint/js';
-import pluginVue from 'eslint-plugin-vue';
 import skipFormatting from '@vue/eslint-config-prettier/skip-formatting';
+import importPlugin from 'eslint-plugin-import';
+import pluginVue from 'eslint-plugin-vue';
+import eslintPluginPrettierRecommended from 'eslint-plugin-prettier/recommended';
 
 export default [
+  js.configs.recommended,
+  ...pluginVue.configs['flat/essential'],
+  skipFormatting,
+  importPlugin.flatConfigs.recommended,
+  eslintPluginPrettierRecommended,
+  {
+    name: 'app/files-to-ignore',
+    ignores: ['**/dist/**', '**/dist-ssr/**', '**/coverage/**'],
+  },
   {
     name: 'app/files-to-lint',
-    files: ['**/*.{js,mjs,jsx,vue}'],
+    files: ['**/*.{js,mjs,cjs}'],
   },
-
   {
-    name: 'app/files-to-ignore',
-    ignores: ['**/dist/**', '**/dist-ssr/**', '**/coverage/**'],
+    files: ['src/**/*.{js,vue}'],
+    rules: {
+      'import/extensions': ['error', 'always'],
+    },
   },
 
-  js.configs.recommended,
-  ...pluginVue.configs['flat/essential'],
-  skipFormatting,
+  {
+    languageOptions: {
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+    },
+    rules: {
+      'no-unused-vars': 'off',
+      'import/no-dynamic-require': 'warn',
+    },
+  },
 ];