jaxtyping v0.2.19

• Proper documentation! Not just markdown files on GitHub any more. Check out https://docs.kidger.site/jaxtyping.
• Added jaxtyping.{PRNGKeyArray,Scalar,ScalarLike}
• Can now nest, e.g.

  Image = Float[Array, "channels height width"]
  BatchImage = Float[Image, "batch"]

• Now packaging in the modern way with pyproject.toml.
• Dtypes can now match regexes (e.g. used in keys to match ^key<\w+>$),

Full Changelog: v0.2.15...v0.2.19