List OOjs UI documentation

Now thanks to I65fe1a78d0b41 we are publishing the documentation for OOjs
UI, we should link to it.

Note that this will need the first patch to get merged since the new task
to publish documentation before we can successfully link to anything, but
that shouldn't be too far off..

Change-Id: Ib159cfed4eb32728db5c2b605bc18e2ea6696a03