Awesome Endeavour: Improve browser related tooling/configs

[hugomrdias]

The main objective of this issue is to keep track of some improvements to browser related features in aegir.
All commands should try to use the related tool cli, to keep behaviour and output standard and don't break user expectations.

Some rules to keep in mind:

• use execa to spawn cli's and return a promise from the cmd handler
• catch/handle errors in yargs fail()
• provide sensible defaults to meet the needs of all repos
• don't break default config resolution from the tools used (normally cosmiconfig or similar)
• allow for overrides/merges using normal config resolution
• allow forwarding command options to the original cli with double dash(--)

• improve browser builds with webpack/babel
• improve karma with new config
• docs: write up docs how to use browser builds (auto and manual for better bundle size)
• docs: include unpkg and jsdeliver in package.json
• docs: package.json files key to reduce npm package size
• make codesandbox and others work out of the box with script tag
• make codesandbox and stackblitz work with npm imports
• browserlist config, support local override using default resolution (envs, queries)
• check if eslint browserlist adds value as a test
• support webpack overrides in .aegir.js
• help with flow setup @vmx (Proposal to move to move to Flow types js-ipfs#1260 and WIP: Flow specific changes #213)
  • https://github.com/flowtype/flow-remove-types
  • mocha support
  • eslint support
  • require hook for dev in /src
• check new webpack-command to replace webpack-cli
• use cosmiconfig directly to test for local config
• uglify config https://github.com/facebook/create-react-app/blob/next/packages/react-scripts/config/webpack.config.prod.js#L413
• try rollup instead of webpack
• add support webpack-bundle-analyzer or source-map-explorer
• add support https://github.com/ai/size-limit
• test chrome on travis ci

Related:

• How to handle packaged modules with webpack #175
• Make dist output usable directly by webpack #210