DEVELOPERS: add Christian Stewart for go

I am now maintaining / submitting regular patches for the Go toolchain as well.

Signed-off-by: Christian Stewart <christian@paral.in>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -469,6 +469,7 @@ F:	package/batman-adv/
 F:	package/docker-containerd/
 F:	package/docker-engine/
 F:	package/docker-proxy/
+F:	package/go/
 F:	package/mosh/
 F:	package/rtl8821au/
 F:	package/runc/