imscJS 2.0.0

Summary of changes since imscJS 1.1.5:

Browser bundle size down reduced by 60% to 15kB!

• uses the native browser DOMParser and removes the sax.js dependency (thanks to @littlespex)
• add support for tts:fontVariant
• move to ES6 modules, typescript definitions and linting (thanks to @littlespex)
• move to modern JS packager and remove Grunt build dependency
• removes conflicts between library symbols and ES symbols
• allow multiple style attributes on element
• improve testing and documentation
• improves generation of reference renders using puppeteer
• improves the reference render comparison script
• Improve ruby rendering across browsers and remove deprecated ruby elements
• Remove symbol conflicts with ECMAScript

Signatures for fromXML(), generateISD(), and renderHTML() remain unchanged.

Deployed at https://www.npmjs.com/package/imsc/v/2.0.0

Full Changelog: 1.1.5...2.0.0