Cache capabilities

[thomasstorm]

This PR fixes #82.

Checklist:

• Issue has been created for change
• Added docstrings and API docs for any new/modified user-facing classes and functions - n.a.
• New/modified features documented in docs/source/* - n.a.
• Changes documented in CHANGES.md
• GitHub CI passes
• Test coverage remains or increases (target 100%)

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (5a4dff9) 91.00% compared to head (bf33dcc) 91.01%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #83      +/-   ##
==========================================
+ Coverage   91.00%   91.01%   +0.01%     
==========================================
  Files          13       13              
  Lines        2457     2461       +4     
==========================================
+ Hits         2236     2240       +4     
  Misses        221      221              

Files Changed	Coverage Δ
tests/core/test_geodb.py	95.40% <100.00%> (ø)
xcube_geodb/core/geodb.py	86.61% <100.00%> (+0.05%)	⬆️

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