Add indentation and folding

[AdrienJaguenet]

Folding seems to be possible with VSCode langage extensions, and it is in my opinion a desirable feature. I am not sure if you can also add virtual whitespaces/tabs to create a visual indentation effect, but I think it would help manual reading of a GEDCOM file as well.

[RokeJulianLockhart]

#2 (comment)

@AdrienJaguenet, can you add here a picture of what you refer to?

[fguitton]

I am planning to update this plugin to align with the latest state of GitHub linguist and add a language server for exactly this sort of thing. Feel free to contribute as well !