v0.27.0 Babel useBuiltIns bug fix & Vue JSX Support!

Zoinks! Another release is ready!

To upgrade:

1. Update your package.json file: set the @symfony/webpack-encore version to ^0.27.0.

2. Run yarn upgrade!

Changes: v0.26.0..v0.27.0

Documentation: http://symfony.com/doc/current/frontend.html

Highlights:

• [Behavior Change] The Babel configuration sourceType default was
  changed from not being specified (so, the default module was used)
  to unambiguous. This is to help Babel's useBuiltIns functionality
  properly determine if a require or import should be automatically
  added to your files, based on that file's style - #555 thanks to @Lyrkan.

• Added JSX support to Vue! #553 thanks to @Kocal.

• Cleaned up the jsdoc in index.js to add better docs and better
  IDE auto-completion - #550 thank sto @Lyrkan.

Happy packing!