added watch mode
slightly changed the start command

* Sync up RapiD and iD esbuild config scripts

* Remove uglify too

* Remove babel/preset-react

* Just have `npm run start` start a modern build, remove `quickstart`

* Better setup for modern/legacy build
- much simpler babel config
- separate entry points for modern and legacy (ie11/phantom)
- explicitly import 'core-js' and 'regenerator-runtime' instead of using deprecated 'babel/polyfill' plugin
- still need 'core-js-bundle' for the test/index.html, so Mocha/PhantomJS combo will work.

* Revert "Better setup for modern/legacy build"

This reverts commit 4ce17de.

Co-authored-by: Milos Brzakovic (E-Search) <mbrzakovic@microsoft.com>