Fix formatting, wording, and typos in docs

[mborland]

Closes: #1185
Closes: #1202

[cppalliance-bot]

An automated preview of the documentation is available at https://1226.decimal.prtest3.cppalliance.org/libs/decimal/doc/html/index.html

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

2025-11-07 13:47:47 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.1%. Comparing base (a6eee1c) to head (776e2c9).
⚠️ Report is 23 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1226     +/-   ##
=========================================
- Coverage     99.1%   99.1%   -0.0%     
=========================================
  Files          262     262             
  Lines        17220   17220             
  Branches      1941    1941             
=========================================
- Hits         17058   17057      -1     
- Misses         162     163      +1     

see 1 file with indirect coverage changes

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