Feature request: Add option for automatic heading numbering

Is your feature request related to a problem? Please describe.
When writing longer documentation, meeting minutes, or structured notes (especially when using Collectives), numbering sections is common practice to easily reference sections across the team. Currently, you have to number headings manually, which makes it quite tedious to keep everything consistent. Whenever an earlier chapter is inserted, deleted, or moved, all subsequent numbers (1.1, 1.2, etc.) have to be adjusted by hand.

Describe the solution you'd like
It would be awesome to have an option for automatic, hierarchical heading numbering (e.g. 1., 1.1, 1.1.1) in the editor and table of contents.

Describe alternatives you've considered
Currently, the only option is updating the numbers manually every time something changes, or skipping numbering altogether (which makes referencing specific sections in team discussions harder).

Additional context
Nextcloud Text is awesome. :)

Start by tracing the editor's heading handling and table-of-contents generation; the issue provides no file or test entry point. Done means an option produces hierarchical numbering such as 1., 1.1, and 1.1.1 consistently in both the editor and table of contents.