Use the raw export string from Showoff.showoff to manipulate axis labels.

[himcraft]

Description

Fixes #2467

Also introduced in my previous PR #4424 . However the previous solution was not elegant. So I submitted a PR for Showoff.jl to add an option exporting the raw strings for RichText.

Ping @jkrumbiegel if you are satisfied with is PR. Please let me know if you have any suggestion for improvement.

Type of change

Delete options that do not apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• Added an entry in CHANGELOG.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.
• Added reference image tests for new plotting functions, recipes, visual options, etc.

[himcraft]

Here is the comparison of the change before and after the modification.

Before:

After: