Introduce BackgroundLayerChooser

[KaiVolland]

Description

This introduces the BackgroundLayerChooser and its childcomponent BackgroundLayerPreview. It`s a combination of an overview map and a layer chooser with an immediate preview.

Pull request type

• [ ] Bugfix
• [x] Feature
• [ ] Dependency updates
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Documentation content changes
• [ ] Other (please describe)

Do you introduce a breaking change?

• [ ] Yes
• [x] No

Checklist

• [x] I understand and agree that the changes in this PR will be licensed under the BSD-2-Clause.
• [x] I have followed the guidelines for contributing.
• [x] The proposed change fits to the content of the Code of Conduct.
• [ ] I have added or updated tests and documentation, and the test suite passes (run npm test locally).
• [x] I have added a screenshot/screencast to illustrate the visual output of my update.