enable import/extensions lint

but paper over a bug in eslint-plugin-import so it doesn't
warn on a false positive.

Author: dynst

eslint.config.mjs

@@ -1,6 +1,7 @@
 import js from "@eslint/js";
 import typescriptEslint from "@typescript-eslint/eslint-plugin";
 import importt from "eslint-plugin-import";
+// eslint-disable-next-line import/extensions
 import prettier from "eslint-plugin-prettier/recommended";
 import simpleImportSort from "eslint-plugin-simple-import-sort";
 import globals from "globals";
@@ -58,6 +59,8 @@ export default [
         },
       ],
 
+      "import/extensions": ["warn", "ignorePackages"],
+
       "simple-import-sort/imports": "warn",
       "simple-import-sort/exports": "warn",
     },