feat: add wmtsDimensions parameter for layer source

[simonseyock]

Description

Adds the wmtsDimensions parameter to the layer source

Related issues or pull requests

terrestris/shogun-util#750

Pull request type

• Bugfix
• Feature
• Dependency updates
• Tests
• 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
• No

Checklist

• I understand and agree that the changes in this PR will be licensed under the
  Apache Licence Version 2.0.
• I have followed the guidelines for contributing.
• 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 mvn test locally).
• I have added a screenshot/screencast to illustrate the visual output of my update.

[simonseyock]

For requestParams the type is HashMap<String, Object>. I suppose it is not a problem to use a more specific type here?

[dnlkoch]

Technically it shouldn't be a problem, but I assume users must pass a string value (in the admin client)? If so it might be confusing since it's possible for the requestParams.