Break out esbuild.CLI public Go CLI API

[earthboundkid]

Refs #152

[earthboundkid]

Copypasta from my own github.com/carlmjohnson/exitcode

[earthboundkid]

Make cmd/esbuild a one liner call into pkg/esbuild, which has a single public function: esbuild.CLI(osargs []string) error. This allows esbuild to be embedded into other Go application without interprocess calls or introducing a new public API beyond the CLI.

[evanw]

I see why you would like to do this. However, I don't think this is a good way to integrate esbuild into other Go apps. There would be no way to programmatically list out build errors, for example. This approach also has other issues such as causing GC to be disabled because esbuild disables GC to improve performance when invoked in batch mode.

Instead of doing this, I'd rather have an API more like the current JavaScript API. That API is future proof like this approach but also more usable. It'd be a much bigger change though, so perhaps not appropriate for a PR.

[evanw]

After a major refactor, the Go CLI is now available in version 0.5.0. I have also added build and transform APIs which are more flexible than the CLI API. The new Go APIs are documented here.

[earthboundkid]

Great!