Create comments to non nostr events

[dluvian]

Describe the enhancement

A EventBuilder function to create nip22 comments to ISBNs, websites, geotags, ..., or any other string.

Use case

Commenting on stuff outside of nostr, like book reviews and youtube comments.

Additional context

https://github.com/nostr-protocol/nips/blob/master/22.md

[dluvian]

Just learned that i and k tag are not just random strings and should follow nip73.

nip22::extract_parent should also be adjusted to support nip73.

[yukibtc]

Just learned that i and k tag are not just random strings and should follow nip73.

nip22::extract_parent should also be adjusted to support nip73.

The nip22::extract_parent already support the NIP73

[TheAwiteb]

Should this be closed? I think it's already resolved since we have CommentTarget::external now