Panning, modeChange Event, minor changes

[olekhshch]

-- prDefault for pressing on mouse wheel to avoid firing of default browser's (e.g. Chrome) panning

-- quick access to the select mode while panning mode is active with dbClick. Also, the panning mode is active while holding Space/mousewheel - once they're released the mode changes back to the previous one. This allows a quicker use of both Select and Panning tools without a need to click them on the left panel.

-- new custom event was added in svgcanvas that fires on every setMode(). For now, the event helps to track the active mode to set cursor styling (atm only zoom, panning, and select tools have their own cursors, but I would like to add it for other tools for better UX). Also, this event can have different implementations in the future.

-- prDefault for Ctrl+wheel - I've added it based on my own experience because I always try to scale the canvas with this shortcut (instead of Shift+wheel), but it scales the whole page instead. Having this behavior here seems unnecessary, perhaps it would be better to allow this shortcut to scale the canvas as well in the future. 👀

-- Ctrl was added to the Undo/Redo shortcuts because theZ shortcut was already assigned for the Zoom tool.

[jfhenon]

The build breaks because of the NYC coverage. The tests are working. Thank you for this PR.