unit bezier curve interpolation
npm install @mapbox/unitbezier
Unit bezier interpolation function: a port to JavaScript from Webkit:
http://svn.webkit.org/repository/webkit/trunk/Source/WebCore/platform/graphics/UnitBezier.h
Initialize a new bezier curve given the points
Evaluate bezier for value x (ranging from 0 to 1) with epsilon precision (1e-6 by default).