Add pre-configured clients, docs fixups

[gadomski]

Turns out that writing docs help make our APIs better, who knew?

Checklist

• Add tests
• Add docs
• Update CHANGELOG

[codecov-commenter]

Codecov Report

Patch coverage: 88.23% and project coverage change: -0.08% ⚠️

Comparison is base (1537fca) 80.47% compared to head (3385461) 80.39%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #74      +/-   ##
==========================================
- Coverage   80.47%   80.39%   -0.08%     
==========================================
  Files          15       15              
  Lines         794      801       +7     
==========================================
+ Hits          639      644       +5     
- Misses        155      157       +2     

Files Changed	Coverage Δ
src/stac_asset/__init__.py	100.00% <ø> (ø)
src/stac_asset/_cli.py	82.99% <ø> (ø)
src/stac_asset/earthdata_client.py	56.00% <ø> (ø)
src/stac_asset/validate.py	100.00% <ø> (ø)
src/stac_asset/client.py	81.92% <60.00%> (-1.83%)	⬇️
src/stac_asset/_functions.py	90.47% <100.00%> (+0.09%)	⬆️
src/stac_asset/http_client.py	57.50% <100.00%> (+2.23%)	⬆️
src/stac_asset/s3_client.py	53.44% <100.00%> (ø)

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