* Add code to shift viewport if mouse is beyond edge
* Allow shifting viewport if mouse is stationary too
* Group all modifier keys into SelectToolPointerKeys
* Cleanup message ordering to remove shifting during resize
* Slow down shifting by half
* Clamp speed; code review cleanup
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Co-authored-by: 0hypercube <0hypercube@gmail.com>
Co-authored-by: Keavon Chambers <keavon@keavon.com>