Use different highlights for markdown titles

[igorlfs]

Is your feature request related to a problem? Please describe.
Treesitter now supports custom highlighting for markdown headers, which would be nice. Current behavior:

Describe the solution you'd like
Using vim's syntax files, we get:

The highlights groups are in format text.title.1.markdown and so on

Describe alternatives you've considered
I could set these highlight groups myself, but I think it benefits the community

[igorlfs]

Thanks!