blendMode BLEND is wrong

Issue description

The docs state:

BLEND - linear interpolation of colours: C = A*factor + B. This is the default blending mode.

But linear interpolation would be C = A*factor + B*(1-factor). As documented it is more like ADD without clamping.

URL(s) of affected page(s)

https://processing.org/reference/blendMode_.html
https://processing.org/reference/blend_.html

Proposed fix

BLEND - linear interpolation of colours: C = A*factor + B*(1-factor). This is the default blending mode.