Timeline providers that don't need URI's should be able to render on empty workbench

[JacksonKearl]

#84297

Currently when the workbench has no ActiveTextEditor, the timeline view won't load anything. But there is a category of "workspace timeline" events that should be able to work without any active editor.

For instance:
Timeline of past/future sprints/iterations
Timeline counting down days till code freeze/GA/etc.
Timeline of git tags/releases

I think the provideTimeline should give an optional uri, and if an extension needs the URI they simply return undefined to be excluded from the timeline. But if not, they can elect to be shown even when theres no active editor.

[eamodio]

💯 I've definitely been thinking about the same thing. Was going to make the uri optional, and am thinking about a UX to toggle the Timeline view into this mode (without having to have no editors open).

[joaomoreno]

@eamodio Moving this to Backlog.

[JacksonKearl]

considering changing timeline provider to accept editor and/or workspace timelines