feat: add CMSShape PDF

[ikrommyd]

Starting a PR to add the CMSShape PDF into zfit-physics.
Related to zfit/zfit#512

Proposed Changes

• Implement CMSShape

Tests added

• tests/test_pdf_cmsshape.py

Checklist

• change approved
• implementation finished
• correct namespace imported
• tests added
• CHANGELOG updated

[jonas-eschle]

Looks good overall, that's the right direction. Docs, (serialization), tests, but you know all that. And as discussed, feel free to add numba-stats as a dependency, that makes sense to test against

[ikrommyd]

@jonas-eschle I'm happy with the current state and testing. Please review it when you got some time.

[jonas-eschle]

Looks good (minus minor things), and you reminded me to also increase the visibility of zfit-physics

[ikrommyd]

@jonas-eschle Alright, let the tests run and merge.

[jonas-eschle]

Looks good! I've just fixed two minor doc things: there was a piece of string laying around in the code and I've converted the docs from MD to RST, which is usually used in Python docstrings (afaik).

[ikrommyd]

Looks good! I've just fixed two minor doc things: there was a piece of string laying around in the code and I've converted the docs from MD to RST, which is usually used in Python docstrings (afaik).

Thanks, I saw md in the relativistic breit wigner implementation so I just followed that. Thanks for removing the string that was lying around, I had forgotten it. Merge it whenever you want!