Implement PgUp and PgDown in the help dialog.

[lroobrou]

Description

The PageUp and PageDown keys weren't doing anything in the help dialog, so I added some lines to make them work.

Issue

Easier navigation in the help dialog.

Testing

I ran cargo test after my changes. For the behavior of the keys themselves, I tested it manually.

• [ ] Windows
• [ ] macOS
• [ x ] Linux

Checklist

• [ x ] Areas your change affects have been linted using rustfmt (cargo fmt)
• [ x ] 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, etc.)
• [ ] The pull request passes the provided CI pipeline
• [ x ] There are no merge conflicts
• [ ] If relevant, new tests were added (don't worry too much about coverage)

[codecov-commenter]

Codecov Report

Base: 18.82% // Head: 18.81% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (1ca5d27) compared to base (b879c36).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #841      +/-   ##
==========================================
- Coverage   18.82%   18.81%   -0.02%     
==========================================
  Files          74       74              
  Lines       13495    13504       +9     
==========================================
  Hits         2541     2541              
- Misses      10954    10963       +9     

Impacted Files	Coverage Δ
src/app.rs	0.00% <0.00%> (ø)

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[ClementTsang]

LGTM, tested on my Macbook.

[ClementTsang]

@all-contributors please add @lroobrou for code.

[allcontributors]

@ClementTsang

I've put up a pull request to add @lroobrou! 🎉