fix(graphql-docs/build): rollup error thrown during build

- during the dts transformation, the css import was not recognized, hence marking it as external in the dts transform didn't throw the error

- "extract: true" in postcss plugin makes sure it gets extracted to the final bundle as well

Signed-off-by: Anik Das <anikdas0811@gmail.com>

packages/bruno-graphql-docs/src/index.ts

@@ -1,6 +1,5 @@
 import { DocExplorer } from './components/DocExplorer';
 
-// Todo: Rollup throws error
 import './index.css';
 
 export { DocExplorer };