Method rect

src/main/java/field/graphics/FLine.java:477–479

draws a rectangle.

(Rect r)

	 * draws a rectangle with corner `x, y` and width `w` and heght `h`
	 */
	public FLine rect(double x, double y, double w, double h) {
		this.moveTo(x, y);
		this.lineTo(x + w, y);
		this.lineTo(x + w, y + h);
		this.lineTo(x, y + h);
		return this.lineTo(x, y);