Keyboard layout tutorials

@david.boddie do you think this documentation is the right place for the documentation on creating keyboard layouts? (API description, tutorials, examples, best practices).

The question comes partially from https://forums.puri.sm/t/translations-and-virtual-touch-keyboards-tracking-localization/7669/36

Another option would be to keep them in the keyboard repository, but then we'd still need a place to upload rendered HTML (and preferably in multiple languages).