[RFC]: Add anglit distribution implementation

### Description

This RFC proposes to add an implementation of the anglit probability distribution to stdlib, following existing continuous distribution patterns.

The anglit distribution has support on [-π/4, π/4] with PDF cos(2x), and is available in SciPy as scipy.stats.anglit.

References:
1. SciPy – https://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.anglit.html

### Related Issues

Related issues # , # , and # .

### Questions

No.

### Other

No.

### Checklist

- [x] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [x] Searched for existing issues and pull requests.
- [x] The issue name begins with `RFC:`.

No file, test, or entry point is named. Start by reviewing the existing continuous distribution patterns in stdlib and the linked SciPy anglit reference, then determine the project’s expected implementation and validation conventions. Done means an anglit distribution implementation is added with support on [-π/4, π/4] and PDF cos(2x).

Rédigé par le modèle d'indexation à partir du texte de l'issue.