Implemented AbstractPullback

[benedict-96]

ZygotePullback is implemented in GeometricMachineLearning (same commit: e638e42), SymbolicPullback will be implemented in SymbolicNeuralNetworks.

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.02%. Comparing base (8366ad1) to head (66df4b5).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/pullback.jl	60.00%	2 Missing ⚠️
src/data_loader/optimize.jl	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #173      +/-   ##
==========================================
- Coverage   68.04%   68.02%   -0.03%     
==========================================
  Files         122      123       +1     
  Lines        3733     3740       +7     
==========================================
+ Hits         2540     2544       +4     
- Misses       1193     1196       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.