feat: adding Hashable conformance to IterationValue

[heckj]

Description

Adds Hashable conformance to IterationValue. Resolves #4

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Minimal checklist:

• I have performed a self-review of my own code
• I have added DocC code-level documentation for any public interfaces exported by the package
• I have added unit and/or integration tests that prove my fix is effective or that my feature works

[codecov]

Codecov Report

Merging #11 (0e53eb5) into main (e9214c5) will increase coverage by 0.02%.
The diff coverage is 98.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
+ Coverage   98.10%   98.12%   +0.02%     
==========================================
  Files           4        4              
  Lines        1631     1649      +18     
==========================================
+ Hits         1600     1618      +18     
  Misses         31       31              

Impacted Files	Coverage Δ
...ests/HistogramTests/HistogramDataAccessTests.swift	99.08% <96.20%> (+<0.01%)	⬆️
Sources/Histogram/Histogram.swift	96.09% <97.14%> (+0.02%)	⬆️
...ests/HistogramTests/HistogramAutosizingTests.swift	100.00% <100.00%> (ø)
Tests/HistogramTests/HistogramTests.swift	100.00% <100.00%> (ø)

Impacted Files	Coverage Δ
...ests/HistogramTests/HistogramDataAccessTests.swift	99.08% <96.20%> (+<0.01%)	⬆️
Sources/Histogram/Histogram.swift	96.09% <97.14%> (+0.02%)	⬆️
...ests/HistogramTests/HistogramAutosizingTests.swift	100.00% <100.00%> (ø)
Tests/HistogramTests/HistogramTests.swift	100.00% <100.00%> (ø)

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[dimlio]

Looks good! Thanks!