This update was in large part created thanks to contributions by immamex , so thanks to them!
**Major Changes**
Added new "custom nfz" parameter to RocketProblems to allow for more fine-grained control of where the frozen point is in the nozzle
While isp, ivac, cf, and mach number would previously be set to 0 when using frozen flow, they are now set to their correct values
Distribution now uses a wheel and pyproject.toml instead of a zip and setup.py
**Small Changes**
Added "nfz" integer parameter and "custom nfz" float parameter to both RocketProblem constructor and set_analysis_type
**Bug Fixes**
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