Update HISTORY.rst and fix docstrings

[tomvothecoder]

Description

• Closes Update doc vars #130
• Closes Fix number 10 for Contributing/Local Development guide #133
• Update HISTORY.rst with v0.1.0 changelog

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 #139 (e50446e) into main (d73d910) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main      #139   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines          341       341           
=========================================
  Hits           341       341           

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

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