Set default charge/spin if not given in .xyz file

[chmwzc]

I got irritated by errors because I kept forgetting to include "0 1" in the comment lines of my .xyz files.
Hence, added code to assume default values of 0 charge and 1 spin-multiplicity if the values weren't found in the .xyz file.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (a0e45f8) 52.16% compared to head (3c79b6d) 51.82%.

Files	Patch %	Lines
src/qibochem/driver/molecule.py	16.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #56      +/-   ##
==========================================
- Coverage   52.16%   51.82%   -0.34%     
==========================================
  Files           8        8              
  Lines         462      465       +3     
==========================================
  Hits          241      241              
- Misses        221      224       +3     

Flag	Coverage Δ
unittests	51.82% <16.66%> (-0.34%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.