Open the API

[01mf02]

This is an effort to make several previously hidden (and potentially duplicated) APIs public, such as:

• compiler diagnostics
• pretty printing
• value reading/writing

As bonus, this PR adds proper pretty printing for YAML:

jaq -n '[1, {a: 2, b: [3]}]' --to yaml
---
- 1
- 
  "a": 2
  "b": 
    - 3
...

Furthermore, it adds support for JQ_COLORS.

[wader]

"bla" as in bla bla bla? 😬🤔

[01mf02]

"bla" as in bla bla bla? 😬🤔

"bla" as in "Better Label Arriving". ;)

I'm not sure yet what exactly should go into this new crate. At the beginning, this was rather small, but now it turns out that extra format support finds a good home here. Just brainstorming: jaq-full, jaq-all, jaq-extra, ...