Starlark imports and multiple converters

Currently you can only import from external starlark files that are already hosted on the drone-convert-starlark service. It would be really cool if The repository being built could also have multiple starlark files. I assume atm you just send the one .star file to drone-convert-starlark however if you sent all the source or maybe all the .star files from the source then drone-convert-starlark could execute pipelines defined by multiple files in the source.

Also you could make it so one could configure multiple convert endpoints. That way a single drone service could offer an extensible choice of different languages in which to define pipelines.