Add region support

[Memphizzz]

Hi!

Thanks for this great extension!
One thing I'm missing is regions, could you add region-folding support like described here:https://code.visualstudio.com/updates/v1_17#_folding-regions ?

That would be awesome!

[TeddyDD]

Honestly I don't know how, and I don't use VScode anymore. I'll update readme stating that I'm looking for maintainer. In the meanwhile I'm happy to merge PR.