Add how to add other language apart from Japanese

[foxmean]

Anyway, Cristian said in discord server that this plugin only work for 1 language. So, should we mentioned about it too? (Not mention yet).

[shiki-tm]

I got Chinese audio files from forvo working through this add on but i had to move all the files to the same folder [forvo_files] where the japanese user folders also are. Especially since Chinese and even many other languages are now being supported by Yomitan, would it be possible to update this add on to have a separate source/folder for other languages like for chinese "zh forvo" or something like that? That way we can just specify in yomitan in the custom url json "language=zh" to only fetch the chinese files. Or at least can you add instructions for how to separate language folders for forvo in the add ons folder? The way it is now, I need to specify all the chinese speakers with forvo usernames in the custom url.

[MarvNC]

I think the overall structure of the readme might need a little more organization but that can come in a later PR.