Scrolling in heading outline

[dragonwolfmastr]

Is your feature request related to a problem? Please describe.
When I create many headings in the Markdown text editor, the outline cannot scroll down to show all of them.

Describe the solution you'd like
Be able to scroll through the document outline when hovering over it with the mouse OR have a scrollbar on the side of the outline.

Describe alternatives you've considered
Make the outline text smaller or move its starting point upward, though this would be a less efficient method.

Additional context

[mejo-]

@luka-nextcloud since I already looked into it briefly: I probably have to set height and overflow-y: auto for .editor--toc:

text/src/components/Editor/TableOfContents.vue

Line 68 in 4d07cbd

.editor--toc {