Add list shortcode titles to TOC

[lbeltrame]

Is your feature request related to a problem? Please describe.
I use multiple lists with different types on the same page, and since some contain quite a number of posts, it would be useful to jump to the one of interest, however the list titles don't appear in a post's TOC.

Describe the solution you'd like
Being able to have the list shortcode titles in the TOC for easier navigation.

Describe alternatives you've considered
Since one can't use empty list titles, I've workarounded this adding a single space as title and using a regular Markdown title above it, however this leaves an ugly empty space where the list title should be.