README: mention the git repo

Change-Id: Ib185a246393d19c57c5a42d0c59e92b0cb4a724d
Reviewed-on: https://go-review.googlesource.com/c/arch/+/625655
Commit-Queue: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>

Author: ianlancetaylor

README.md

@@ -8,8 +8,10 @@ The parts needed in the main Go repository are copied in.
 ## Report Issues / Send Patches
 
 This repository uses Gerrit for code changes. To learn how to submit changes to
-this repository, see https://golang.org/doc/contribute.html.
+this repository, see https://go.dev/doc/contribute.
+
+The git repository is https://go.googlesource.com/arch.
 
 The main issue tracker for the arch repository is located at
-https://github.com/golang/go/issues. Prefix your issue with "x/arch:" in the
+https://go.dev/issues. Prefix your issue with "x/arch:" in the
 subject line, so it is easy to find.