Make esbuild options available to plugins

[thomaschaaf]

It would be good if the plugins could access the esbuild options. E.g. I would like to access the tsconfig passed in.

Currently they are not available see: https://esbuild.github.io/plugins/#load-arguments

[evanw]

Yes, I agree. I plan to do this but still haven't done it yet. Closing as a duplicate of #373.

[evanw]

Support for this is in the latest release. Documentation is here: https://esbuild.github.io/plugins/#build-options.