Add a place for translations of the documentation to the source tree

[Richard Boulton]

Yung-chung Lin has translated the intro_ir.html document into zh_TW. It would be good to have a place in the source tree to put such documents.

[Olly Betts]

FWIW, we can't really include his translation as it stands - the licence is ​http://creativecommons.org/licenses/by-nc-nd/3.0/ which doesn't allow commercial use or modification - both restrictions are contrary to the DFSG, for example. I imagine if we point out the problem that he'd be willing to use a more appropriate licence though.

For suitably licensed contributions, I think docs/zh_TW would be a good place to put them.

[Olly Betts]

The newer documentation is built with Sphinx and hosted with readthedocs (​https://getting-started-with-xapian.readthedocs.io/en/latest/) - they support a sensible looking way to have translations of the docs - e.g. a zh_TW translation would have the same URLs but with /zh_TW/ in place of /en/ at the start of the path:

​https://docs.readthedocs.io/en/stable/localization.html

So we do now have a place for translations of the documentation - people can create a branch in the repo for each translation and we can go from there. I think that addresses this ticket, so I'm going to close it.