[FEATURE] Add Right Click to Shortcut documentation

Is your feature request related to a problem? Please describe. It was hard to figure out how to pan across a large diagrame (>100 tables). Found out from the Issue tracker that right clicking toggles a grab and pan mouse mode.

Describe the solution you'd like Please note in the Shortcuts (linked from the app) documentation that Right clicking allows paning the diagram.

Additional context Would note that on Chrome, right clicking initally opens a popup menu, and the pan mode doesn't always activate.