Consolidate and tidy examples

[magland]

#97 should be merged first

Tidy up the examples directory. Now it only contains four examples that are clearly labeled, corresponding to the four examples in the readme.

There is also a benchmark1.py example that compares write times between zarr, lindi, hdf5, and dat formats.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.13%. Comparing base (9183af9) to head (bdcd402).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
- Coverage   69.07%   67.13%   -1.95%     
==========================================
  Files          34       30       -4     
  Lines        3046     2796     -250     
==========================================
- Hits         2104     1877     -227     
+ Misses        942      919      -23     

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