v0.12.2: infrastructure

This release fully supports ES6 modules. LaTeX.js itself has not changed, but the build system and the docs have improved a lot.

exports:

• no default export anymore, export: he, parse, Generator, HtmlGenerator

build:

• simplified rollup config and build
• added visualizer
• generate correct source maps
• get rid of all eval calls
• use dynamic imports for external packages and documentclasses

unit tests:

• update to puppeteer 3.3, now we can start to support Firefox screenshots
• added a script to create a native LaTeX rendering for the test cases
• updated mocha
• support and fix code coverage

docs:

• moved to VuePress
• use a git worktree in the website folder to generate the docs and playground in the gh-pages branch