fix: don't try to check types in JS

lib/eslint.mjs

@@ -93,20 +93,8 @@ const makeEslintConfig = ({ tsconfigRootDir, globals: globalsIn } = {}, ...moreC
   return tseslint.config(
     // Start with recommended rules from ESLint and TypeScript ESLint.
     {
-      extends: [
+      extends: [eslint.configs.recommended, tseslint.configs.recommended, tseslint.configs.stylistic],
-        eslint.configs.recommended,
-        tsconfigRootDir ? tseslint.configs.recommendedTypeChecked : tseslint.configs.recommended,
-        tsconfigRootDir ? tseslint.configs.stylisticTypeChecked : tseslint.configs.stylistic,
-      ],
       languageOptions: {
-        parserOptions: {
-          ...(tsconfigRootDir
-            ? {
-                projectService: true,
-                tsconfigRootDir,
-              }
-            : {}),
-        },
         ...(globalsIn ? { globals: flattenedGlobals } : {}),
       },
     },
@@ -229,19 +217,27 @@ const makeEslintConfig = ({ tsconfigRootDir, globals: globalsIn } = {}, ...moreC
 
         // https://typescript-eslint.io/rules/no-non-null-assertion
         '@typescript-eslint/no-non-null-assertion': ['error'],
-
+      },
-        // Rules that require type information
+    },
-        ...(tsconfigRootDir
+    tsconfigRootDir
       ? {
+          files: ['**/*.ts', '**/*.tsx', '**/*.mts', '**/*.cts'],
+          extends: [tseslint.configs.recommendedTypeChecked, tseslint.configs.stylisticTypeChecked],
+          languageOptions: {
+            parserOptions: {
+              projectService: true,
+              tsconfigRootDir,
+            },
+          },
+          rules: {
             // https://typescript-eslint.io/rules/no-unnecessary-condition/
             '@typescript-eslint/no-unnecessary-condition': ['error'],
 
             // https://typescript-eslint.io/rules/require-await/
             '@typescript-eslint/require-await': ['error'],
+          },
         }
-          : {}),
+      : {},
-      },
-    },
     // @eslint-community/eslint-plugin-eslint-comments
     {
       extends: [