Add featuretools-sklearn-transformer back as an optional install

[rwedge]

Fixes #1606

Adds the featuretools[sklearn] optional install configuration and adds documentation about it

[codecov]

Codecov Report

Merging #2335 (9fa5857) into main (23ba744) will increase coverage by 34.03%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main    #2335       +/-   ##
===========================================
+ Coverage   65.35%   99.38%   +34.03%     
===========================================
  Files         177      177               
  Lines       18773    18773               
===========================================
+ Hits        12269    18658     +6389     
+ Misses       6504      115     -6389     

Impacted Files	Coverage Δ
featuretools/feature_base/feature_base.py	98.15% <0.00%> (+0.20%)	⬆️
featuretools/entityset/timedelta.py	98.41% <0.00%> (+0.79%)	⬆️
featuretools/entityset/relationship.py	98.83% <0.00%> (+1.16%)	⬆️
featuretools/utils/wrangle.py	79.71% <0.00%> (+2.89%)	⬆️
featuretools/tests/testing_utils/features.py	100.00% <0.00%> (+3.70%)	⬆️
featuretools/tests/testing_utils/es_utils.py	100.00% <0.00%> (+4.34%)	⬆️
...s/computational_backends/feature_set_calculator.py	98.69% <0.00%> (+4.45%)	⬆️
featuretools/config_init.py	97.82% <0.00%> (+6.52%)	⬆️
featuretools/utils/gen_utils.py	100.00% <0.00%> (+7.24%)	⬆️
featuretools/computational_backends/feature_set.py	100.00% <0.00%> (+7.47%)	⬆️
... and 48 more

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