Extend Gilda's grounder

[cthoyt]

This PR makes a subclass of gilda's grounder that has some more convenient functions and data structures

[codecov]

Codecov Report

Attention: 20 lines in your changes are missing coverage. Please review.

Comparison is base (d7ee99b) 42.98% compared to head (15a237e) 44.32%.

Files	Patch %	Lines
src/biolexica/api.py	46.87%	17 Missing ⚠️
src/biolexica/web.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #9      +/-   ##
==========================================
+ Coverage   42.98%   44.32%   +1.33%     
==========================================
  Files          12       12              
  Lines         342      361      +19     
  Branches       65       61       -4     
==========================================
+ Hits          147      160      +13     
- Misses        188      194       +6     
  Partials        7        7              

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