Update become-committer.md (#819)

Add reference to Gerrit ReAuth guide.

Author: mitchella-google

src/docs/become-committer.md

@@ -12,7 +12,7 @@ A committer is a contributor to the V8 project’s success and a citizen helping
 
 *Note to Googlers: There is a [slightly different approach for V8 team members](http://go/v8/setup_permissions.md).*
 
-If you haven't done so already, **you'll need to set up a Security Key on your account before you're added to the committer list.**
+If you haven't done so already, **you'll need to set up a Security Key on your account before you're added to the committer list.**.  For more information about this requirement see [Gerrit ReAuth](https://chromium.googlesource.com/chromium/src/+/main/docs/gerrit_reauth.md).
 
 In a nutshell, contribute 20 non-trivial patches and get at least three different people to review them (you'll need three people to support you). Then ask someone to nominate you. You're demonstrating your: