Added Richard Gibson as co-champion

Author: erights

README.md

@@ -8,7 +8,7 @@ A TC39 proposal for immutable ArrayBuffers.
 
 **Stage**: 0
 
-**Champion**: Mark S. Miller (@erights), Peter Hoddie (@phoddie)
+**Champion**: Mark S. Miller (@erights), Peter Hoddie (@phoddie), Richard Gibson (@gibson042)
 
 **Specification**: https://papers.agoric.com/tc39-proposal-immutable-arraybuffer/