vendor/transformation-matrix/skew.js
function skew(ax, ay) {
    return {
        a: 1, c: tan(ax), e: 0,
        b: tan(ay), d: 1, f: 0
    };
}
function skew(ax, ay) {
    return {
        a: 1, c: tan(ax), e: 0,
        b: tan(ay), d: 1, f: 0
    };
}
function skew ( ax , ay ) { return { a : 1 , c : tan ( ax ) , e : 0 , b : tan ( ay ) , d : 1 , f : 0 } ; }
Calculate a skew matrix
@param ax Skew on axis x
@param ay Skew on axis y
@returns {{a: number, b: number, c: number, e: number, d: number, f: number}} Affine matrix
Calculate a skew matrix