Tree view for nested dirs

[FloSch62]

We should enable a tree view for nested dirs
like it would be great if we would have a tree structure so we can open up the labs that I have in my ./private and hide the rest
in the source control tab they do this with this handy icon
it switches from list to tree view

[FloSch62]

@hellt actually I am not really sure if I understood the request

[hellt]

if you have clab files layed out as

• red/lab1.clab.yml
• blue/lab2.clab.yml
• blue/lab3.clab.yml

then it would be great to have a file tree in the panel, so that not all labs appear in the flat fashion and you could open blue dir to see the two labs (2 and 3) there