Add triggerrer avatar information in prebuilds

[gtsiolis]

Problem to solve

Back in #4970 we added prebuilds pages. However, these pages didn't include triggerrer avatar information for each prebuild. 🧑‍🚀

Follow up issue from #4958, point 13. See also #4876 (comment).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[gtsiolis]

This is still relevant. Cc @jldec