docs: add array shape dimensions to Normal distribution type hints

[professor314]

Summary

Adds jaxtyping shape annotations to the Normal distribution class, replacing bare Array type hints with Float[Array, " *shape"] where appropriate.

Changes

• Import Float from jaxtyping
• Annotate loc and scale fields as Float[Array, " *shape"]
• Annotate all method parameters and return types with shape dimensions
• support returns Float[Array, ""] (scalar bounds)
• All other methods use Float[Array, " *shape"] matching the event shape

Motivation

Addresses #35. Shape-annotated type hints make the API clearer for users reading docs or using IDE autocompletion, and enable more precise runtime checking via beartype in tests.

This PR covers the Normal distribution as a starting point. The same pattern can be applied to other distributions in follow-up PRs.

Testing

Type-annotation-only change. No behavioral changes. The existing test suite (normal_test.py) continues to pass.

[lockwo]

needs formatting

[professor314]

Hey, sorry about the formatting. I ran the project's Black formatter and pushed a fix. I saw issue #35 and thought the Normal distribution would be a good starting point since it's the most commonly used one. Let me know if there's anything else that needs adjusting.