Add gpgkeys repo to the announce template

[igaw]

Luis has this snippet in his announcement emails:

All keys used for the uploads can be found on the following git repository:

   git://git.kernel.org/pub/scm/docs/kernel/pgpkeys.git

Let's add it to template.

[igaw]

Make it a bit easier to understand. Suggestion by Steven:

• All keys used for the above files and repositories can be found on the following git repository
• All keys used for the above files and repositories can be found in this git repository

[igaw]

Updated to the first version.