Creates and returns a linear gradient. Parameters (sx, sy) (ex, ey) specify the start and end coordinates
of the linear gradient, icol specifies the start color and ocol the end color.
The gradient is transformed by the current transform when it is passed to fillPaint or strokePaint.
NVGPaintlinearGradient(NVGContext ctx, float sx, float sy, float ex, float ey, Color icol, Color ocol)
Creates and returns a linear gradient. Parameters (sx, sy) (ex, ey) specify the start and end coordinates of the linear gradient, icol specifies the start color and ocol the end color. The gradient is transformed by the current transform when it is passed to fillPaint or strokePaint.