Add ability to sort ScopedKeys

[dotsdl]

Closes #198.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (76c439c) 82.25% compared to head (2d8aa18) 82.32%.

Files	Patch %	Lines
alchemiscale/models.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #199      +/-   ##
==========================================
+ Coverage   82.25%   82.32%   +0.07%     
==========================================
  Files          22       22              
  Lines        2739     2739              
==========================================
+ Hits         2253     2255       +2     
+ Misses        486      484       -2     

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[dotsdl]

@ianmkenney can I get a review from you on this one? No rush.

[ianmkenney]

LGTM

[dotsdl]

@ianmkenney danke! Merging!