Link Previews should take Anchor/Fragment into account

Currently the link previews always show the top of the page. This is fine when linking to the top of a page, such as:

https://en.wikipedia.org/wiki/Discord_(software)

But, when you are linking to something further down the page, say:

https://en.wikipedia.org/wiki/Discord_(software)#Software

You get the same preview as you'd get without the #Software.

Pulling the preview text from the start of the referenced element (id="Software" in this case, or if not found, the first name="Software" should it exist) would make the preview more relevant to those clicking on it.

This comes up frequently when linking to specific posts on a forum, such as Sufficient Velocity, where the anchor/fragment may be there directly:

https://forums.sufficientvelocity.com/threads/mauling-snarks-worm.41471/page-170#post-10232301

Or added via redirect:

https://forums.sufficientvelocity.com/posts/10232301/

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