Implement and register CallHierarchyProvider

[ghost]

First, thank you for an awesome extension. I use it regularly and it's miles ahead of its alternatives.

As of VSCode 1.33 there's a proposed API for providing call hierarchies.
Can this extension register as a Call Hierarchy Provider? This would make use of VSCode's UI, and I thought it wouldn't be that hard since this extension already has this functionality.

I apologize for not submitting a PR, I'm not familiar with TypeScript in general, and VSCode extensions in particular.
Resources that may be helpful:

• https://github.com/microsoft/vscode-extension-samples/tree/master/call-hierarchy-sample
• https://github.com/jrieken/demo-callhierarchy

Thanks!

[MaskRay]

VSCode has its own hierarchy implementation: src/hierarchies/. I have expressed my opinions about VSCode's design but apparently they were not considered...

I have seen textDocument/callHierarchy on https://microsoft.github.io/language-server-protocol/specifications/specification-3-16/ There is no children property and tags?: SymbolTag[]; references a type SymbolTag which is not really defined...

Currently there is insufficient information to implement this stuff, I think...

[ghost]

Thank you for your response.
I'll look into it if I have the time in the future.