[diagram] DoubleClick open the code editor and not the diagram editor

[lmcbout]

From the workspace navigator, double click on a file open the code version of the selection. If I selected the "Open With -> Yang Diagram" previously, I would expect the second time I open the file to use the "Yang Diagram" and not the code editor. May we can have a preference for "Double Click opening the editor"

[JanKoehnlein]

That seems to be a Theia issue: Remember the last open handler used.