README: mention the git repo

Change-Id: Id01077e4708b481e42b5aab6a34c25d6e34d1fe0
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/625397
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

README.md

diff --git a/README.md b/README.md
index 48253c6..5e5a025 100644
--- a/README.md
+++ b/README.md
@@ -24,9 +24,11 @@
 
 --
 
-Contributions to Go are appreciated. See https://golang.org/doc/contribute.html.
+Contributions to Go are appreciated. See https://go.dev/doc/contribute.
 
-* Bugs can be filed at the [Go issue tracker](https://golang.org/issue/new?title=x/mobile:+).
+The git repository is https://go.googlesource.com/mobile.
+
+* Bugs can be filed at the [Go issue tracker](https://go.dev/issue/new?title=x/mobile:+).
 * Feature requests should preliminary be discussed on
 [golang-nuts](https://groups.google.com/forum/#!forum/golang-nuts)
 mailing list.