[NOTICE] Moving away from the repo by the end of the year

[tqchen]

Thanks everyone for working together in this effort. As we are moving more developments upstream, it would be good to keep a timeline when we completely switchs to upstream development.

Considering the current state, let us plan to move to away from this repo by the end of 2021

[junrushao]

No objection from me.

First, The repo has been out-of-sync for a while due to the heavy engineering effort to rebase; Second, as we have planned, things on this repo will be refactored and upstreamed by the end of this year. Therefore, there is no major reason to work on it any more.