Add example of using esbuild

[cmdcolin]

Large plugins may result in a slow 'refresh cycle' (waiting on rollup to recompile the single file umd bundle)

Could potentially investigate using esbuild

Alternatively or in addition to this, add plugin dev environment that uses @jbrowse/react-app

Vite uses a combo of esbuild (at dev time) and rollup (for prod builds) as an example

[cmdcolin]

Example large plugins...apollo, proteinview3d (large molstar package)