Add ability to add a Panel through an extension

[sandy081]

Requested by @dakaraphi in #41071

When a tree view is shown, it should be predictable where it is shown. This is why I think they all need to be on their own panel. If I want to view bookmarks, I don't want it maybe open at the bottom of the explorer, or the middle or who knows where because I have 5 or 6 other tree view contributions.

[sandy081]

Contributing to activity bar is implemented here - #43645

Changing this to contribute to panel only

[simonhaenisch]

Just to clarify: is this a request for allowing to contribute new panels (with custom web views), i. e. next to "Problems", "Output", "Debug Console" and "Terminal"?

One thing I was looking to do was to add a place to put down notes by contributing a "Notes" tab in the panels area, and rendering a custom view in there (similar to what the terminal does).

[sandy081]

Yes

[nbransby]

I have a use case to add a 'debug console'-like view to the panel, is this feature planned anytime soon?