Outline (toc) remove headings from `details` Block

[janbaum]

Describe the bug
If Headings are used in a details block, they also appear in the outline (table of contents)

To Reproduce
Steps to reproduce the behavior:

1. create detail block
2. create headings in details-block body
3. show outline
4. see headings from inside detail block in outline

Expected behavior
Don't show those headings from details in outline, since people probably want to hide this content anyway with the detail block. E.g I put longer instructions in there, to not overload my files. The instructions have lots of heading, say 10, while the actual file has only 5 headings. Showing the outline bloats out with 15 headings, which is not what I would expect I think (?)