chat: updating the CONTRIBUTORS file
chat: updating the CONTRIBUTORS file

The CONTRIBUTORS file is no longer needed for the submission
automation, but it is still required as per the open source
requirements. This CL updates the CONTRIBUTORS file header and
populates its content with the current list of contributors.

MultiPart: 6/9
Change-Id: If67d347743a1ac3f9cc25bd2fbc44450a335a79b

vanadium/chat,vanadium/chat,viksit/chat,vanadium/chat,viksit/chat,vanadium/chat,vanadium/chat,viksit/chat,viksit/chat,viksit/chat