Docs fixes

[bwohlberg]

Fix a variety of docs issues, including missing documentation for scico.numpy submodules.

[codecov]

Codecov Report

Merging #420 (ec7892f) into main (14d041e) will decrease coverage by 0.10%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##             main     #420      +/-   ##
==========================================
- Coverage   94.85%   94.76%   -0.10%     
==========================================
  Files          83       86       +3     
  Lines        5290     5309      +19     
==========================================
+ Hits         5018     5031      +13     
- Misses        272      278       +6     

Flag	Coverage Δ
unittests	94.76% <78.57%> (-0.10%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
scico/flax/blocks.py	100.00% <ø> (ø)
scico/flax/examples/data_generation.py	74.10% <ø> (ø)
scico/flax/examples/data_preprocessing.py	94.96% <ø> (ø)
scico/flax/inverse.py	98.64% <ø> (ø)
scico/flax/models.py	100.00% <ø> (ø)
scico/flax/train/spectral.py	100.00% <ø> (ø)
scico/flax/train/state.py	100.00% <ø> (ø)
scico/flax/train/trainer.py	93.95% <ø> (ø)
scico/numpy/_wrappers.py	91.02% <25.00%> (-7.66%)	⬇️
scico/numpy/__init__.py	100.00% <100.00%> (ø)
... and 3 more