Markdown Editor & draggable sub tasks

TL;DR

• Added a Markdown editor and removed unused dependencies

• Adjusted MD Preview

• Adjusted sub tasks to be draggable

• New MD Preview:

• New MD Editor:

• Draggable sub tasks:

Details

TODO:

• [ ] Make sub tasks editable

Checklist / Reminders:

• [ ] Documentation is created / adapted
• [ ] Unit Tests