`Chore`: Migrate to different Markdown library

[FelberMartin]

Description

The currently used markwon library has not been updated since 3 years and does not support image loading with coil3.

https://github.com/mikepenz/multiplatform-markdown-renderer seems like a good candidate, with active development and support for coil3.

Steps

• Replace usages of Markwon with the new library
• Ensure everything still works (links, images, basic text markup, ...)
• Remove dependency on coil2