Add property for all editor tabs to vscode.window namespace

[PaulTFreedman]

I was looking at writing an extension that changed the active tab when a mouse scroll event is detected but there don't appear to be any properties exposed that allow access to all the open tabs (editors). There is a property called activeTextEditor which contains the editor with focus and another one called visibleTextEditors which contains all the editors visible to the user. I would like another property that contains all of the text editors that the user has open.

For example if there is only 1 editor group open containing 3 files then the property would contain 3 elements.

[bpasero]

please report VSCode issues here: https://github.com/Microsoft/vscode/