Update themed CSS

[cwisniew]

Identify the Bug or Feature request

Resolves #4187

Description of the Change

Adds the following to the themed CSS

  --mt-theme-panel-background: ...;
  --mt-theme-panel-foreground: ...;

  --mt-theme-progress-bar-arc: ...;
  --mt-theme-progress-bar-background-color: ...;
  --mt-theme-progress-font-family: ...;
  --mt-theme-progress-font-size: ...;

  --mt-theme-scroll-bar-background-color: ...;
  --mt-theme-scroll-bar-show-buttons: ...;
  --mt-theme-scroll-bar-thumb-highlight-color: ...;
  --mt-theme-scroll-bar-thumb-arc: ...;
  --mt-theme-scroll-bar-thumb-border-color: ...;
  --mt-theme-scroll-bar-thumb-shadow-color: ...;
  --mt-theme-scroll-bar-thumb-dark-shadow-color: ...;
  --mt-theme-scroll-bar-thumb-color: ...;
  --mt-theme-scroll-bar-thumb-insets-left: ...;
  --mt-theme-scroll-bar-thumb-insets-top: ...;
  --mt-theme-scroll-bar-thumb-insets-right: ...;
  --mt-theme-scroll-bar-thumb-insets-bottom: ...;

Also updated comments where missing in CSS extraction classes and changed constructor for the classes to accept function to format the colour rather than directly using static method of another class

Possible Drawbacks

Hopefully none

Documentation Notes

  --mt-theme-panel-background: ...;
  --mt-theme-panel-foreground: ...;

  --mt-theme-progress-bar-arc: ...;
  --mt-theme-progress-bar-background-color: ...;
  --mt-theme-progress-font-family: ...;
  --mt-theme-progress-font-size: ...;

  --mt-theme-scroll-bar-background-color: ...;
  --mt-theme-scroll-bar-show-buttons: ...;
  --mt-theme-scroll-bar-thumb-highlight-color: ...;
  --mt-theme-scroll-bar-thumb-arc: ...;
  --mt-theme-scroll-bar-thumb-border-color: ...;
  --mt-theme-scroll-bar-thumb-shadow-color: ...;
  --mt-theme-scroll-bar-thumb-dark-shadow-color: ...;
  --mt-theme-scroll-bar-thumb-color: ...;
  --mt-theme-scroll-bar-thumb-insets-left: ...;
  --mt-theme-scroll-bar-thumb-insets-top: ...;
  --mt-theme-scroll-bar-thumb-insets-right: ...;
  --mt-theme-scroll-bar-thumb-insets-bottom: ...;

Release Notes

• Added further CSS entries to themed CSS

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This change is