First pass at setting up the metacrate

[cmyr]

This is a very barebones starting point (not trying to be too fancy with features, not trying to figure out how to test.)

• does the readme look good?

• do we want to try and figure out some tests that pass types from one crate into another, where those types are part of the public API?

• HarfRust is currently on an older version of read-fonts, so that should get updated before we publish

• this doesn't expose all of the different subfeatures of the different crates. For instance, there's no way to turn off traversal, and no way to turn of std. I think this is maybe reasonable, and the story can be that if you really need fine-grained control you can go and assemble exactly the stack you need manually? I feel like in the general case the users of this crate are going to be less fiddly? But correct me if I'm wrong.

• this still needs CI

• closes Setup metacrate #1

[rsheeter]

note: two different versions of crate read_fonts are being used; two types coming from two different versions of the same crate are different types even if they look the same

This is nice. If it's easy an even nicer version would be to have the version check as it's own job so we see Continuous integration / consistent dependency versions failed directly on the PR. That's just nice to have tho.

[rsheeter]

there's no way to turn off traversal, and no way to turn of std

I don't want traversal on by default. I'd be ok with punting on no-std until we have a specific use case.

[rsheeter]

harfrust and skrifa (the most likely problemmatic pairing) or harfrust, skrifa, klippa would be a better exmaple.

[rsheeter]

I suggest we land this and file issues for followups. It's fine that CI is temporarily busted.