Update Documentation in Conformance to the Documentation Guide

[PSchmiedmayer]

Problem

The current documentation in the module provides a good overview of the API and includes documentation for most public APIs. In line with the newly published Stanford Spezi Documentation Guide, we should update the documentation in accordance with the guidelines.

Solution

The documentation should be updated to provide more insightful inline documentation, improve the README file and the DocC landing page in conformance with the Stanford Spezi Documentation Guide.

• [x] Update inline documentation, including links and other elements noted in the Code Documentation section.
• [x] Improve the DocC landing page as detailed in the Landing Page section.
• [x] Add a graphic and visual representation of the module user interface (UI) or UML diagram of the architecture or interacting with the module API.
• [x] Improve the READMe as noted in the README section.

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct and Contributing Guidelines

[PSchmiedmayer]

The only element left here, is adapting the links to the new version of Spezi, e.g., the renamed Setup tutorial that will be released with the next Spezi version and once the documentation is build on the Swift Package Index: https://swiftpackageindex.com/StanfordSpezi/Spezi

• [x] Update Links and check that all are accurate

[vishnuravi]

This has been completed!