tests: added basic for layouts

[maximelucas]

• added initial tests for layout functions
• added seed argument for layout functions that did not have it

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +1.49 🎉

Comparison is base (c72af43) 82.01% compared to head (a26575d) 83.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #293      +/-   ##
==========================================
+ Coverage   82.01%   83.50%   +1.49%     
==========================================
  Files          35       35              
  Lines        2691     2698       +7     
==========================================
+ Hits         2207     2253      +46     
+ Misses        484      445      -39     

Impacted Files	Coverage Δ
xgi/drawing/layout.py	78.26% <100.00%> (+65.35%)	⬆️

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[nwlandry]

Looks great! Thanks so much! Having the seed arg will make life SO much easier.