Add a "Outline: Show Regions" option

[Plasma3]

In the settings, under Features > Explorer, there are multiple Outline: Show X options that allows you to customize what symbols are shown in the outline.

I want the following option to be added:

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Outline: Show Regions

• [ ] When enabled, Outline shows region-symbols

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It adds regions, with everything between region name_of_region and endregion being indented under the region, in the outline.