[llvm-foundation] Please document the monorepo policy

[David Chisnall via llvm-foundation]

Dear Foundation,

As you are taking the lead in the GitHub move, please can we have some official documentation of the policy for what is going to be included in the monorepo?  My understanding, based on mailing-list discussions and in-person discussions with other developers, including those at EuroLLVM, was that everything that is version-locked to LLVM would be in a monorepo, everything else would remain in separate repos.  Apparently this is not the case.  Please will you explicitly clarify what is intended as the final outcome?

David