Improve h-entry fetch function

[grantcodes]

At the moment it's not great.

Maybe it should just use x-ray but I like being independent

Features it needs:

• [ ] Find h-card if not on post
• [ ] Relative links -> absolute links
• [ ] Save files to the media endpoint? (fixes https issues but may be a lot of extra storage - maybe a flag)
• [ ] Improve getting data from other meta tags
• [ ] Improve embed grabbing