Compatibility with the Code Outline extension

[Pign]

Symbols are not reported as a tree (following conversation with @Gama11 it seems it's because the entire definition range is not reported).

This is problematic when using the code outline extension.

[Gama11]

Details: https://github.com/patrys/vscode-code-outline#language-support

[Gama11]

VSCode is actually adding a built-in code outline as well, see microsoft/vscode#5605 (comment). I think this will require the same changes on our end though.

[Gama11]

Vshaxe 2.2.0 will support hierarchical document symbols! 🎉 Here's an example (the outline of the document symbol implementation itself):

This also means that we support the breadcrumbs view that's being added in VSCode 1.26. Here's a screenshot from a current Insider's build:

[nadako]

the breadcrumbs view

this looks sweet!

[Gama11]

It has these nice dropdowns too. ;)