Zoom In / Out on Electron

[garrettmflynn]

It would be great to have a zoom in/out option in the Electron app so that users can avoid tables that clip.

I've started a branch (https://github.com/NeurodataWithoutBorders/nwb-guide/tree/zoom-shortcut) that explores this idea. However, it seems like the required CommandAndControl + numsub command, as well as any others that have shortcuts like numadd and numsub, will not work on my Mac—otherwise this would be a fairly straightforward feature to implement

[CodyCBakerPhD]

Summarized and moved to #846

Re-open again whenever this starts active development