feat: Add Codable conformance

[hassila]

Description

Add Codable constraint/conformance allowing automatic synthesising of Codable so Histograms can be serializes/deserialized.

Also commented out test code that was not used yet.

How Has This Been Tested?

Just added the constraint and run test suite.

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 #6 (d83f6fd) into main (49df02b) will increase coverage by 0.12%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #6      +/-   ##
==========================================
+ Coverage   97.98%   98.10%   +0.12%     
==========================================
  Files           4        4              
  Lines        1631     1631              
==========================================
+ Hits         1598     1600       +2     
+ Misses         33       31       -2     

Impacted Files	Coverage Δ
Sources/Histogram/Histogram.swift	96.08% <ø> (ø)
...ests/HistogramTests/HistogramAutosizingTests.swift	100.00% <100.00%> (+3.08%)	⬆️

Impacted Files	Coverage Δ
Sources/Histogram/Histogram.swift	96.08% <ø> (ø)
...ests/HistogramTests/HistogramAutosizingTests.swift	100.00% <100.00%> (+3.08%)	⬆️

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