[dev.typeparams] codereview.cfg: add config for dev.typeparams

The codereview command will start using this to figure out
the origin branch for commands like "git pending",
and it will use the parent setting for the new "git branch-sync" (merge).

Change-Id: Ia74af18ae5a437fb45ea81d7d69e2ffe41987b64
Reviewed-on: https://go-review.googlesource.com/c/go/+/279523
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

codereview.cfg

@@ -0,0 +1,2 @@
+branch: dev.typeparams
+parent-branch: dev.regabi