When used with Spinx / docutils, allow inserting nodes at the upper level

[lumag]

Describe the feature you'd like to request

I have a main .rst file, which then uses include:: foo.md / :parser: myst_parser.sphinx_ to include the MarkDown document. The MarkDown document is supposed to be a complete section (including the section title), however per the documentation MyST pushes parsed document under the current section (as a subsection). While it is possible to add new section for the MD file in the main document, it also brings undesirable side effect of a duplicate section (and subsection headers).

Cut-down example:

• main.rst:

******************
CI-tron Components
******************

The executor service
====================

some text of the section


.. include:: salad/README.md
   :parser: myst_parser.sphinx_

• salad/README.md

# SALAD
some other texxt

Resulting section structure:

# CI-tron Components
## The executor service
### SALAD

Desired section structure:

# CI-tron Components
## The executor service
## SALAD

Describe the solution you'd like

No response

Describe alternatives you've considered

No response