dot function
Calculates the dot product of two vec3's
@param {ReadonlyVec3} a the first operand @param {ReadonlyVec3} b the second operand @returns {Number} dot product of a and b
Implementation
double dot(List<double> a, List<double> b) {
return a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
}