Add CLI option to list available export names

[flying-sheep]

I can do

python -c 'import nbconvert; print(*nbconvert.exporters.get_export_names(), sep=" ")'

but that’s not very discoverable

[MSeal]

I agree. That would be a nice, quick addition.

[rahulpshah]

Is this still an issue?

nbconvert/nbconvert/nbconvertapp.py

Line 184 in 8b47cf1

Options include {0}

[flying-sheep]

Oh! well, I didn’t find that there. Should be inline in the --to param docs, too.

[MSeal]

I too missed with a quick look since the examples are far away from the --to option. @flying-sheep you could make a PR to update that commands description fairly easily.