Import @tilgovi's dom-anchor-* libraries

[BigBlueHat]

This has been part of the plan since day one (or earlier 😉).

Now that we've got our npm org up and running, let's close this loop.

@tilgovi are you still able to make this happen?

See #25 (comment)

[tilgovi]

Definitely.

[tilgovi]

I propose we bump this out of the first release. Let's just get the basics. I'm not yet sure whether those packages have the right API for us.

[Treora]

Relatedly, as I just wrote on the dev mailing list:

Do you have, or else shall we perhaps create, an overview of the modules we want to create, and how they relate to each other? That way we would have a clear reason why we have and maintain each module. In the attached graph, I sketched the relations between the mentioned modules (as I understand them), while already adding two hypothetical candidates in grey.

But as the dev mailing list appears not to support attaching images, I hope it helps if I post the graph here:

[Treora]

Just discussed in the weekly call: rather than importing these modules as such, we better just get at (and beyond) feature parity and thereby make them obsolete.

For the missing functionalities see their relevant issues:

• dom-anchor-text-position: see Support TextPositionSelector (in the dom package) #75
• dom-anchor-text-quote: we lack fuzzy matching, see Fuzzy text quote matching #83
• dom-anchor-fragment: does anybody actually use this? Open an issue if so. :) (it seems Hypothes.is dropped it)