Restored JIT functionality

3.0.1 (5/25/2025)

• fix JIT regression (thanks @avgeiss)
• clarify polarization in docstrings
• improve README.rst
• fix git branches
• rename mie.mie_scalar to mie.single_sphere
• rename small_mie_sphere to small_sphere
• rename small_conducting_mie to small_conducting_sphere
• rationalize importing of jit and non-jit code
• add test_jit_speed.py and test_nojit_speed.py