Repack with Zopfli

A proof-of-concept. Doesn't upload any files; everything happens in the browser. See npm/rfcs#595.

1. Get a tarball of your favorite npm package with npm pack $PACKAGE_NAME. For example, try npm pack express.
Select it here:
Zopfli should run iteration(s). More iterations takes longer, but improves compression
Click to start the process