Take a look at NIP-30. These kind of links should be in a tag with mediatype.. Same for images.
Discussion
Oh lol, really. I'll check it out
No client does this yet, afaik. I want to make some test events soon.
NIP-30 seems like a good idea but doesn't seem to have gained too much traction from client devs. Discussion has stalled in the PR as well.
I added experimental support for NIP-30 to nostr-tool on the latest main branch if someone wants to play around with it. Adheres to the current PR but that is probably subject to change.