Mermaid output window

I've noticed a slight problem with Mermaid output:

Mermaid output is always rendered to 100% of the viewer. This is a serious problem when the diagram is huge.

I'd suggest to add a viewer window when double-clicking the diagram. This window should have 2 options:

  • allow to set the canvas size (not the window) thus the window must have scrollbars
  • button to make canvas size equal to the window size

The window itself should be resizable and remember size and position.