feat: add support for SQLModel

[hadrien]

Problem

• People who use SQLModel cannot use FastSQLA

Solution

• Support SQLModel
• Update CI to use tox and test with and without SQLModel

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (8e58a8b) to head (5a19ea3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #18   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           95       100    +5     
  Branches         6         6           
=========================================
+ Hits            95       100    +5     

Flag	Coverage Δ
default	100.00% <100.00%> (?)
sqlmodel	98.00% <71.42%> (?)

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