`point.offset(dx [, dy])`

Offset the point (change its `x`

and `y`

coordinates) by `dx`

in x-axis and `dy`

in y-axis.

If only `dx`

is specified and is a number, `dy`

is considered to be zero. If only `dx`

is specified and is an object, it is considered to be another point or an object in the form `{ x: [number], y: [number] }`