feature: support bold text

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (such as any change that modifies the UI), please provide screenshots of the changes:

Support bold text as a styling configuration option.

Issue

If applicable, what issue does this address?

Closes: #556

Testing

If relevant, please state how this was tested. All changes must be tested to work:

If this is a code change, please also indicate which platforms were tested:

• Windows
• macOS
• Linux

Checklist

If relevant, ensure the following have been met:

• Areas your change affects have been linted using rustfmt (cargo fmt)
• The change has been tested and doesn't appear to cause any unintended breakage
• Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• The pull request passes the provided CI pipeline
• There are no merge conflicts
• If relevant, new tests were added (don't worry too much about coverage)

[ClementTsang]

TODO (maybe in another PR): change header to use default bold?

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 41.27%. Comparing base (f091ebd) to head (c36ce62).

Files	Patch %	Lines
src/options/config/style/utils.rs	93.33%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1512      +/-   ##
==========================================
- Coverage   41.80%   41.27%   -0.54%     
==========================================
  Files         110      113       +3     
  Lines       17276    17685     +409     
==========================================
+ Hits         7223     7299      +76     
- Misses      10053    10386     +333     

Flag	Coverage Δ
macos-12	36.72% <93.33%> (+0.31%)	⬆️
ubuntu-latest	43.25% <93.33%> (+0.25%)	⬆️
windows-2019	36.89% <93.33%> (?)

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