remove ext-name, it sucks

it would return old/unknown extensions (such as `.arts`) as video or image for no reason

src/modules.d.ts

@@ -3,8 +3,6 @@ declare module '*.module.css' {
   export default classes;
 }
 
-declare module 'ext-name';
-
 declare module 'lodash';
 
 declare module 'react-draggable';