Support Webpack and/or Rollup (for better tree-shaking)

[NfNitLoop]

ESBuild was easy to set up as a plugin, but it currently has a bug/limitation that re-exports (which are a recommended pattern in Deno deps.ts files) aren't properly removed by tree-shaking.

Add support for Webpack and/or Rollup to support better tree-shaking.

Additionally:

• One of those might let me specify whether/how to chunk external dependencies?

[NfNitLoop]

Spent some time investigating swc's spack as an alternative here (because speedy) but:

• docs are not great
• it doesn't resolve remote modules and I don't see a way to configure/implement that.

😞