Signed-off-by: Enrico Lefass <[email protected]>

The german translation of presentation.md was updated, since it was effectively a copy of the english documentation.

Update the german pomodoro.md as it was effectively a copy of the english one.

Change description of citations to matching first headline in the document.

Updating the german readabilityy.md since it was effectively a copy of the english documentation.

Fix the link to the https://zettlr.com/readability.

Update german translation of customm-templates.md as it was effectively a copy of the english documentation.

Update de.yml matching the first header of the german translation in custom-templates.md.

Replacing core with Kern.

Add german translation of concepts with context.md, workspaces.md and wysiwym.md.

Update german translation of custom-templates.md to catch up with english version.

Fix typo in graph.md and add missing png.

Add missing png for custom-templates.md.

Update the german translation of the guidessection as it was essentially in english. guide-ide.md and guides-notes.md were translated so the sectionis now complete.

Add german translation of documentation of the core.