lottietoqml: Implement support for skew/shear animations

This is currently not handled because we need to map between the "angle of skew" and "angle of direction" parameters we get in Lottie and the "factor along x" and "factor along y" we have in Qt Quick.

Hopefully it can be solved as

xFactor = tan(angle of direction) * cos(angle of skew)
yFactor = tan(angle of direction) * sin(angle of skew)

But this also needs some testing.