Add basic cmdline parsing and help output

[danielhollas]

Help is on the way!

$ openfms --help
OpenFMS: Ab initio Multiple spawning for the masses

cmdline options:

  -h, --help       print help and exit
  -v, --version    print version

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.26%. Comparing base (e1be80b) to head (beff66b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   54.13%   54.26%   +0.13%     
==========================================
  Files          42       42              
  Lines        5980     5998      +18     
  Branches      800      800              
==========================================
+ Hits         3237     3255      +18     
  Misses       2395     2395              
  Partials      348      348              

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