add bold text styling options

[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:

(WIP)

Adds the ability to use bold text via config to table headers, general text, widget titles, graph legends, and graph axis. By default, they're all off for now, but I'll probably make some of them default in a future PR.

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)

[codecov]

Codecov Report

Patch coverage: 30.76% and project coverage change: -0.16 ⚠️

Comparison is base (78b1126) 21.47% compared to head (202648a) 21.31%.

❗ Current head 202648a differs from pull request most recent head 8abcc8d. Consider uploading reports for the commit 8abcc8d to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1019      +/-   ##
==========================================
- Coverage   21.47%   21.31%   -0.16%     
==========================================
  Files          75       75              
  Lines       14604    14754     +150     
==========================================
+ Hits         3136     3145       +9     
- Misses      11468    11609     +141     

Impacted Files	Coverage Δ
src/canvas.rs	0.00% <0.00%> (ø)
src/components/data_table/styling.rs	9.09% <0.00%> (ø)
src/widgets/cpu_graph.rs	0.00% <0.00%> (ø)
src/widgets/disk_table.rs	0.00% <0.00%> (ø)
src/widgets/process_table.rs	14.35% <0.00%> (+0.23%)	⬆️
src/widgets/temperature_table.rs	0.00% <0.00%> (ø)
src/bin/main.rs	36.58% <100.00%> (-0.74%)	⬇️
src/canvas/canvas_styling.rs	45.80% <100.00%> (ø)
src/options.rs	41.94% <100.00%> (ø)

... and 7 files with indirect coverage changes

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[ClementTsang]

Closing this in favour of another PR.