Add a doc for the proposed update protocol
Add a doc for the proposed update protocol

Relevant to the discussion in #95

modelorganism/xi-editor,google/xi-editor,google/xi-editor,google/xi-editor,google/xi-editor,fuchsia-mirror/third_party-xi-editor,modelorganism/xi-editor,fuchsia-mirror/third_party-xi-editor,modelorganism/xi-editor,fuchsia-mirror/third_party-xi-editor,fuchsia-mirror/third_party-xi-editor