Handle non-finite values in naturalsize

[AnishPatel526]

Changes proposed in this pull request:

• naturalsize() now handles non-finite input consistently with the rest of the library. Every numeric formatter in humanize.number (ordinal, intcomma, intword, apnumber, fractional, scientific, clamp) already returns "NaN" / "+Inf" / "-Inf" for non-finite values via _format_not_finite. naturalsize() was the exception: naturalsize(float("nan")) raised ValueError: cannot convert float NaN to integer, and naturalsize(float("inf")) produced the bogus string "inf QB". It now returns "NaN" / "+Inf" / "-Inf".
• Added a parametrized test_naturalsize_non_finite covering nan, inf, -inf as both floats and strings; it fails on main and passes with this change.

Before

>>> import humanize
>>> humanize.naturalsize(float("nan"))
ValueError: cannot convert float NaN to integer
>>> humanize.naturalsize(float("inf"))
'inf QB'

After

>>> humanize.naturalsize(float("nan"))
'NaN'
>>> humanize.naturalsize(float("inf"))
'+Inf'
>>> humanize.naturalsize(float("-inf"))
'-Inf'

The fix reuses the existing humanize.number._format_not_finite helper so output matches the other formatters exactly, and guards right after the float(value) conversion. Finite values are unaffected.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.57%. Comparing base (3201e70) to head (d205f65).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #390   +/-   ##
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  Coverage   99.56%   99.57%           
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  Files          12       12           
  Lines         927      934    +7     
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+ Hits          923      930    +7     
  Misses          4        4           

Flag	Coverage Δ
macos-latest	97.64% <100.00%> (+0.01%)	⬆️
ubuntu-latest	97.64% <100.00%> (+0.01%)	⬆️
windows-latest	95.50% <100.00%> (+0.03%)	⬆️

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[hugovk]

Closing as duplicate of of #299.

Check for duplicates yourself next time.