It would be nice to have a simple way for plugins to provide additional data export formats. Might require a bit of work on the internals. I can work around this at a lower level with the prepare_sanic hook from #437 in the mean time.

I guess plugins should be able to register a function which takes a row or list of rows and returns the rendered data. They'll also need to provide a file extension and probably a Content-Type.

Datasette could then automatically include this format in the list of export formats on each page.

Looks like this is related to #119.