feat: MTK Jacobian for CoupledDEs

[oameye]

resolves #228

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.43%. Comparing base (6c98239) to head (8fd4b0e).
Report is 34 commits behind head on main.

Files with missing lines	Patch %	Lines
ext/src/CoupledSDEs.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #229      +/-   ##
==========================================
+ Coverage   82.00%   86.43%   +4.42%     
==========================================
  Files          15       17       +2     
  Lines         717      936     +219     
==========================================
+ Hits          588      809     +221     
+ Misses        129      127       -2     

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