feat: add hint around canvas panning

[dwelle]

Many users don't know how to pan canvas. While we will add a separate pan tool shortly, we should nevertheless teach people how to move canvas in a more efficient way.

Added a hint around canvas panning, when a selection tool is active, but nothing is selected — the reasoning for the latter is we show specific hints when certain elements are selected (arrow, line...) or when doing some action while selection tool is active (resizing...). So it's best we don't show the canvas panning hint all the time as it'd not be consistent and to ensure the hint doesn't appear as related to selecting.

Not showing on Mobile. This will still show on tablets. We will need a better way to discern devices that don't have a keyboard or mouse attached. One way is to detect in which way the selection tool was selected (pointerType/keyboard) — we're already doing that for image tool, but we need to figure out a state management for this so it propagates to HintViewer.

[vercel]

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