webpack polyfills did not work because useBuiltIns: 'entry' expects a
explicit core-js import. Changed it to 'usage' which does not require
these explicit imports and polyfills based on browserslist.
As a result, the built index.js now went from 128kB to 192kB.
Ref: https://babeljs.io/docs/en/babel-preset-env#usebuiltins
- moved gitgraph.js to web_src and made it importable and es6-compatible
- created new webpack chunk for gitgraph
- enabled CSS loader in webpack
- enabled async/await syntax via regenerator-runtime
- added script to ensure webpack chunks are loaded correctly
- disable terser's comment extraction to prevent .LICENCE files
gitgraph.js has many issues:
1. it is incompatible with ES6 because of strict-mode violations
1. it does not export anything
1. it's css has weird styles like for `body`
1. it is not available on npm
I fixed points 1-3 in our version so it's now loadable in webpack. We should eventually consider alternatives.
* modernize js and use babel
- add babel toolchain to transform modern JS to ES5
- extend eslint config for modern rules
- fixes linting issues via `eslint --fix` and manual fixes
* run 'make css' to satisfy CI
* code style tweaks and set js indendation to 2 in .editorconfig
* regenerate js
