Update the Rose Pine theme family, including new syntax overrides
matching the official theme docs:
https://rosepinetheme.com/palette/ingredients/

Also adds a doc to our internal docs starting to outline how our syntax
highlighting works.

Before:
<img width="626" alt="CleanShot 2023-06-21 at 12 19 17@2x"
src="https://github.com/zed-industries/zed/assets/1714999/5ebe1cd0-1707-483b-a50f-bb53dbf89ba2">

After:
<img width="718" alt="CleanShot 2023-06-21 at 12 18 48@2x"
src="https://github.com/zed-industries/zed/assets/1714999/46b588aa-31a0-4402-934b-e3de7bc2f6b5">

From their site:

![image](https://github.com/zed-industries/zed/assets/1714999/83d4f671-e15f-4423-a01e-b382145e79fb)


Release Notes:

- Updated Rose Pine theme family to better match original theme.