Move away from create-react-app

[JasoonS]

There are various limitation to using create-react-app. For starters it puts a limitation that all source files need to be nested in the src folder. The other is that it is slow.

A proposal would be to move to esbuild, which is orders of magnitude faster than webpack (which create-react-app uses)

This isn't a super important issue - but needed before moving to a 'mono-repo' shared library style rescript setup.
https://github.com/sikanhe/rescript-esbuild-starter