Add divergence and updates

[kthyng]

• hopefully fixing issue reordering dimensions when extra coords present
• divergence calculation was added to derived.py
• accessor changes:
  • xgrid is run automatically when accessor is used, which could be too slow for some uses
  • div and div_norm properties added to accessor
  • div_norm is the surface divergence normalized by f
• added tests for new functions
• hopefully fixed build issue on several OSes by pinning h5py < 3.2, see for reference https://github.com/h5py/h5py/issues/1880, https://github.com/conda-forge/h5py-feedstock/issues/92
• updated docs

[codecov-commenter]

Codecov Report

Merging #47 (f65e4e0) into main (4c71c07) will increase coverage by 0.03%. The diff coverage is 85.71%.

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@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   84.30%   84.33%   +0.03%     
==========================================
  Files          17       17              
  Lines        1797     1839      +42     
==========================================
+ Hits         1515     1551      +36     
- Misses        282      288       +6     

Flag	Coverage Δ
unittests	84.33% <85.71%> (+0.03%)	:arrow_up:

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

Files Changed	Coverage Δ
xroms/__init__.py	81.25% <ø> (ø)
xroms/utilities.py	88.42% <ø> (ø)
xroms/xroms.py	58.48% <14.28%> (-1.15%)	:arrow_down:
xroms/accessor.py	74.80% <100.00%> (+1.38%)	:arrow_up:
xroms/derived.py	99.13% <100.00%> (+0.09%)	:arrow_up:
xroms/tests/test_accessor.py	98.98% <100.00%> (+0.01%)	:arrow_up:
xroms/tests/test_derived.py	100.00% <100.00%> (ø)

[kthyng]

Can't figure out how to fix the Ubuntu 3.11 build error nor get xESMF to be recognized so the interp page of the docs will run.