Strip hash from chunk file name

Created by: esturcke

Fix

This fixes bug #3048 (closed) and strips hashes from chunks correctly.

Testing

1. npm run create-react-app test-fix
2. cd test-fix
3. Copied src/App.js and src/content.js from cra-chunk-bundle-diff-bug repo
4. yarn build

...
File sizes after gzip:

  48.61 KB  build/static/js/main.b6cc0832.js
  288 B     build/static/css/main.cacbacc7.css
  177 B     build/static/js/content.4f2061bf.chunk.js
...

5. Edit src/content.js
6. yarn build

...
File sizes after gzip:

  48.61 KB (-1 B)  build/static/js/main.b3f3c0af.js
  288 B            build/static/css/main.cacbacc7.css
  180 B (+3 B)     build/static/js/content.c58cbe0c.chunk.js
...