0.11.0 emits Rollup warning about missing dependency

[yaymukund]

Updating from 0.10.0 to 0.11.0, I see a new error:

Rollup warning:  'whatwg-fetch' is imported by tmp/rollup_with_dependencies-cache_path-3qZzcypG.tmp/src/index.js, but could not be resolved – treating it as an external dependency

To import whatwg-fetch, I just did:

// in package.json
"whatwg-fetch": "^2.0.3"

// in index.ts
import 'whatwg-fetch';

Please let me know if you need any more info ^^