Use babel loose mode

[Andarist]

This reduces bundle size a little bit (thanks to loose mode) and keeps babel configs in sync between babelrc and rollup.config.js

es bundle size went down from 2097 to 1903 (gzipped, not minified)
umd.min bundle size went down from 1525 to 1405 (gzipped, minified)

Those numbers assumes ofc that #2 is merged in.

[codecov]

Codecov Report

Merging #3 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master     #3   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           2      2           
  Lines          37     37           
  Branches       16     16           
=====================================
  Hits           37     37

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[erikras]

Published in v1.0.1.

dist/react-final-form-html5-validation.es.js went from 730K to 5.4K. 😱