Support zooming in preview, because some output graphs is unreadable without zooming

[tungdaomissmpeu]

As title, example I have a graph looks like this

It is really hard to see what is on the graph, even if I use a big, high resolution monitor.
So it would be nice if the previewer have a zoom button, or zoom on Ctrl + MouseScroll

[mvbukov]

I agree, zooming is needed. I have sequence diagrams which are rather long. Current preview is too small.