Summary:
This allows breaking changes in Litho to be landed.
I'm also adding some helpers to determine if Flipper itself
is currently in a release or snapshot release train.
N.B. We don't publish snapshot releases for Flipper
right now, but will in the future where this will come in
handy.
Reviewed By: jknoxville
Differential Revision: D9359035
fbshipit-source-id: d21b607eca5d57caf4cc34234f6ba3cb0d8f307d
cded1ceead