Need accelerator key to open the Yarn Diagram

[lmcbout]

In the "Yang Diagram" navigator, double click open the "code editor", but there is other way to open the diagram directly from the navigator and open the "Yarn Diagram" than selecting through the menu selection. There is no accelerator key.

[JanKoehnlein]

Seems to be more Theia related: Allow to choose among openers with a certain keybinding. We should discuss that in Theia.