[Playground] Replace rollup browser with esbuild-wasm

[jchavarri]

We currently use rollup to bundle the resulting JS in a worker:

https://github.com/melange-re/melange-re.github.io/blob/aea0e11ac12bafef07d0286f71fbf2e828a4d97a/playground/src/worker.js#L79

I suspect esbuild-wasm will be much faster than rollup. cc @denis-ok as the esbuild expert :)

[jchavarri]

Docs: https://esbuild.github.io/api/#browser

Example usage