Add core.typed and Timbre recipies

[frenchy64]

3 core.typed recipes and one Timbre.

Can we add a chapter for verification? core.typed doesn't really fit into testing.

[mcfilib]

👍

[levand]

Ambrose,

Great recipes! Thanks so much for your submissions.

A couple notes before I merge this:

• I don't think we'll have enough material to add a full chapter on verification. While you're right that it's not really testing, either, I think it will have to go in the testing chapter, with a caveat in the problem statement mentioning that it's really a runtime correctness guarantee, not a separate test phase. This is also true of things like pre- and post-conditions, so I don't think that will be a huge problem. Is that ok with you?
• There are a few stylistic discrepancies from the rest of the recipes; you use a very conversational "We do this... what happens?" style. In general, most of the recipes are a bit more declarative than interrogative (thought that can be context-dependent), and use the second person (you) rather than first person (we) plural pronoun. If you want, you can make these changes, otherwise we will, as part of the editing process. Just wanted to give you a heads up that that might be happening (unless you think the style is critical to preserve, and we should talk about it first)

Thanks!

[frenchy64]

I'm totally fine with wherever the core.typed material goes.

Feel free to edit the style to your needs.