CONTRIBUTORS: update for the Go 1.16 release

This update was created using the updatecontrib command:

	go get golang.org/x/build/cmd/updatecontrib
	cd gotip
	updatecontrib

With manual changes based on publicly available information
to canonicalize letter case and formatting for a few names.

For #12042.

Change-Id: I030b77e8ebcc7fe02106f0f264acdfb0b56e20d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/291189
Trust: Carlos Amedee <[email protected]>
Run-TryBot: Carlos Amedee <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Alexander Rakoczy <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: cagedmantis