Add faster Half Cauchy

[rohanbabbar04]

Description

• Add HalfCauchy with all methods.

• Add test in test_scipy.py.

• Add HalfCauchy to docs.

  • [x] Code style is correct (follows pylint and black guidelines)
  • [x] Includes new or updated tests to cover the new feature
  • [x] New features are properly documented (with an example if appropriate)

[rohanbabbar04]

The tests will fail there is an if statement, lemme replace it with cdf_bounds

[aloctavodia]

Thanks, I read it very quickly and I missed the if statement! thanks for fixing it.