Add geospatial averaging

[tomvothecoder]

Description

This PR is a refactoring effort of PR #87, feature/46-spatial-averaging

• Closes Add grid-aware geospatial averaging (weighted) #46

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

If applicable:

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass with my changes (locally and CI/CD build)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have noted that this is a breaking change for a major release (fix or feature that would cause existing functionality to not work as expected)

[codecov-commenter]

Codecov Report

Merging #95 (dd47623) into main (2ed55a7) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              main       #95    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            5         6     +1     
  Lines          146       286   +140     
==========================================
+ Hits           146       286   +140     

Impacted Files	Coverage Δ
xcdat/__init__.py	100.00% <ø> (ø)
xcdat/bounds.py	100.00% <100.00%> (ø)
xcdat/spatial_avg.py	100.00% <100.00%> (ø)
xcdat/xcdat.py	100.00% <100.00%> (ø)

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[tomvothecoder]

Hey @pochedls, I squashed the commits recently so your version of this branch may be really out of date. To simplify things, you can checkout main, delete this branch, and checkout the latest version of this branch.

It would be great if you can address the TODO: comments in spatial_avg.py. I'm currently in the process of writing tests as well.

Summary of Recent Changes:

• Updated the name of the decorator for the spatial averaging accessor from ds.avg.spatial to ds.spatial.avg
• Updated the parent file name from averager_accessor.py to spatial_avg.py
• Added xcdat.py, which includes the XCDATAccessor to store all of our public accessor methods under a single namespace.
  • Spatial averaging can be accessed by ds.spatial.avg or ds.xcdat.spatial_avg
• On PR Update open_dataset and dataset_keep_vars() to limit dataset to only 1 variable #105, xcdat.open_dataset() now limits datasets to a single variable

[tomvothecoder]

TODOs from 9/29 meeting
@pochedls

• Finish up TODOs for code documentation
• Finish up QA of tests
• Make axis arg in avg() default to `["lat", "lon"]