Feature Request: Tree view

[jonasglass]

It would be awesome to include a very common way of viewing YANG models: Yang tree view.
This is the graphical representation of YANG modules which is used in most of the RFCs. Pyang offers this feature of doing this via CLI. However, I envision yangster to offer this representation as well, enhanced with navigation features when clicking on it. I know this is similar to the already existing "outline" tab, but nevertheless I am sure that this will bring benefits. It could be implemented as a new diagram.

Example from an RFC:
https://tools.ietf.org/html/rfc7223#section-3

RFC regarding the syntax of Yang tree view:
https://www.rfc-editor.org/rfc/pdfrfc/rfc8340.txt.pdf

What do you guys think about it?