Links, paths, and anchors

[pdaoust]

Resolves #467

Seeking review for:

• Succinctness of prose -- do you get lost? Is there too much information, is the complex stuff (e.g., introducing how to get a hash for linking) introduced too early?
• Correctness of code at first glance -- I have to confess I haven't tried compiling any of it yet.

[mjbrisebois]

Looks great. I didn't know how to use the anchor functions until reading this.

[mattyg]

awesome stuff thanks for taking this on!

[mattyg]

Thrilled with this, amazing work

[pdaoust]

@mattyg thanks so much for all the encouragement -- glad to hear it's landing 🙏🏼 I've been out of programming for so long that positive feedback is very welcome. And I think I'm getting the hang of writing Rust code (and hApp code), although there are some gnarly things along the way (e.g., holochain/holochain#4575 ).

I've tried compiling all the code samples and discovered that there were a fair few errors; would you be willing to re-review this PR and make sure my 'solutions' to the errors are all reasonably idiomatic?

[mattyg]

couple issues in comments, otherwise looks good.

[mattyg]

🔥 🔥