docs: Add GitHub link

Change-Id: Icc14922426060f21d602d4081c2bae7368223d98
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/37220
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Keir Mierle <keir@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/README.md b/README.md
index b3ada79..872db60 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,8 @@
  - [Chat room (Discord)](https://discord.gg/M9NSeTA)
  - [Open Source blog post](https://opensource.googleblog.com/2020/03/pigweed-collection-of-embedded-libraries.html)
 
-Get the code: `git clone https://pigweed.googlesource.com/pigweed/pigweed`
+Get the code: `git clone https://pigweed.googlesource.com/pigweed/pigweed` (or
+[fork us on GitHub](https://github.com/google/pigweed)).
 
 # Getting Started