feat(lib): add index support

[Nivl]

TODO:

• Add doc
• Implement index read-only
• Implement extensions read-only
• Add tests
• Implement writing index (should probably be in another PR)

[codecov]

Codecov Report

Merging #167 (d6d8a9d) into main (4bc5326) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #167   +/-   ##
=======================================
  Coverage   82.33%   82.33%           
=======================================
  Files          29       29           
  Lines        2757     2757           
=======================================
  Hits         2270     2270           
  Misses        345      345           
  Partials      142      142           

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