85b110e041
This adds a note requesting that additions of new ops to the Vector dialect go through an RFC process. The goal is to clarify expectations for contributors. Note: this documents an existing (though previously unwritten) convention. See, e.g.: * https://discourse.llvm.org/t/rfc-adding-vector-to-elements-op-to-the-vector-dialect * https://discourse.llvm.org/t/rfc-improving-gather-codegen-for-vector-dialect