[BREAKING CHANGE] Depend on OOjs v2.1.0, up from v2.0.0
[BREAKING CHANGE] Depend on OOjs v2.1.0, up from v2.0.0

This is a breaking change as it alters the requirements on downstream
users of the library to provide an environment with the new version.

Change-Id: I47a312631004bf2d9ecfa8302b9554dd59317b1f

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui