feat(resources): direct link / enumeration of YouTube videos

[mrmundt]

Summary

The resources "Learn" page doesn't truly reflect how many previous seminars, videos, tutorials, etc., we have posted. It would be nice to be able to get that information from YouTube more directly or at least have a pointer to our YouTube channel / different playlists.

Requirements

• Link to US-RSE YouTube Channel (either embedded or a simple hyperlink, or something more fancy)
• Include the YouTube videos in the "Seminars in archive" counter