- added new 'make webpack' target
- deprecated 'make js' and 'make css'
- extend webpack config to load the less files
- updated docs

I had to rename the source file of `arc-green.less` to avoid generating
a useless JS entrypoint via webpack-fix-style-only-entries which would
not work with different source/destination filenames. I hear that there
should be cleaner solutions possible once we upgrade to Webpack 5.

Co-authored-by: zeripath <art27@cantab.net>

This changes the CSS output of webpack to output to the public/css
directory instead of inling CSS in JS. This enables CSS minification and
autoprefixer based on browserslist which would otherwise not be
possible.

The result of this change is two new output files currently:

- public/css/swagger.css
- public/css/gitgraph.css

Co-authored-by: techknowlogick <matti@mdranta.net>

- reduce verbosity during build
- use array form `use` to allow easier extension
- disable uninteresting source maps
- disable symlink resolution for a speedup

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <matti@mdranta.net>

Currently, this needs to be its own chunk because fomantic depends
on jQuery being present. The next step is to move fomantic to webpack
too after which we can combine the index,fomantic and jquery files into
one.

jquery-migrate is still neccessary because our ancient version of Dropzone
seems to break without it. I imagine it can be removed after a Dropzone
upgrade.

Created a second webpack output file for swagger-ui which is loaded on
the /api/swagger route. One notable difference is the absence of the
swagger favicon that was previously used which is now the gitea icon. I
see no easy way to restore that favicon, so I decided to not keep it.

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

Co-authored-by: zeripath <art27@cantab.net>

- 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.

* pack web_src/js/draw.js to public/js/index.js

* fix eslint

* 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

* Move index.js to web_src and use webpack

* Fix initHeatMap

* update eslint and move webpack to devDependencies

* update index.js

* add eslint env node