Enable the use of themes for editor styling information

[numeredev]

DESCRIPTION

What does your feature request improve on? Please describe.
Although changing the styling of syntax elements is possible in editor, exchanging such configurations is harder than it should be. The usage of themes in their respective file formats would be helpful.

Describe the solution you'd like
Enable themes via theme files (which might be ini-files themselves). Individual settings of such themes should be customizable changing the used theme to "custom". Themes should be savable as well.

Additional context
Add any other context or screenshots about the feature request here.

(Do not write below this line)

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DEVS' SECTION

ANALYSIS

(Describe, what's the issue and which changes have to be made)

IMPLEMENTATION STEPS

(see also our Wiki for implementation guidelines)

• Implement the necessary changes in a new branch created here on GitHub
• Test your implementation

DOCUMENTATION STEPS

(see also our Wiki for further information)

• Update the changes log
• Add comments to your implementation
• Add Doxygen documentation comments
• Create or update the documentation articles (*.NHLP and *.NDB files, if needed)
• Update the language strings (*.NLNG files, if needed)

PULL REQUEST

• Create a pull request for your changes
• Fill out the template
• Assign @numere-org/maintainers as reviewers