Allow a translation directory over the rootModule concept.

[toastal]

I would like to put a translations folder my project folder and elm-i18n --src . --rootModule Translation --translations-directory ./app-translations which would build from that directory into the --src ., using the root module name. Or I can put the folder elsewhere, but it looks like rootModule is pulling double duty as both the outputted module name AND the the location. Since this is just moving around symlinks, why make it work like this? Surely other people have some alternative link directories (like maybe a submodule or another project).