Add fastcore.style: fast styling for friendly CLIs

[seeM]

cc @hamelsmu @jph00

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[jph00]

I like it! Two suggestions:

1. Inherit from, or (maybe better?) compose, list, not L, to avoid dep on foundation
2. Put this in its own module -- since it'll be used in a lot of CLIs, we want it fast, so no reason to import all of xtras

Also, can you check whether Quarto now supports ansi terminal escapes? If it does, we should stop removing them all in processors.py.

[seeM]

@jph00 Done, I like your suggestions! In my testing, it doesn't seem like Quarto supports ansi terminal escapes yet.