Add endian transformation functions

[mborland]

Closes: #492

[cppalliance-bot]

An automated preview of the documentation is available at https://495.int128.prtest3.cppalliance.org/libs/int128/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-08-03 15:43:17 UTC

[codecov]

Codecov Report

❌ Patch coverage is 98.79518% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.25%. Comparing base (22729a2) to head (043c74b).
⚠️ Report is 8 commits behind head on develop.

Files with missing lines	Patch %	Lines
test/test_byte_conversions.cpp	97.82%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #495      +/-   ##
===========================================
+ Coverage    95.15%   95.25%   +0.09%     
===========================================
  Files           97      100       +3     
  Lines         8916     9165     +249     
  Branches      3297     3388      +91     
===========================================
+ Hits          8484     8730     +246     
- Misses          78       81       +3     
  Partials       354      354              

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