Is your feature request related to a problem? Please describe.
In the editor screen of Gutenberg is already a "Table of Contents" (named "Content structure") implemented. It would be nice to have the same feature in the frontend!

Describe the solution you'd like
Make already existing "Content structure" available as "Table of Contents" Block.

Describe alternatives you've considered
Using a "Table of Contents" Plugin like in pre-Gutenberg times.