Allow a size of 0 in area's rectangle state

This makes it so that an area's rectangle state can have
rectangles with a width or height of 0, by allowing the top left corner to be identical to the bottom right instead of having to
be strictly smaller.

This makes it consistent with the other two states, as circles
are allowed to have a radius of 0 and polygons can have all
their points along a line or even in a single spot, making
areas with a size of 0 possible.

Fixes whatwg#10306.

source

@@ -41878,11 +41878,12 @@ interface <dfn interface>HTMLAreaElement</dfn> : <span>HTMLElement</span> {
 
   <p>In the <dfn attr-value for="area/shape" data-x="attr-area-shape-rect">rectangle state</dfn>,
   <code>area</code> elements must have a <code data-x="attr-area-coords">coords</code> attribute
-  with exactly four integers, the first of which must be less than the third, and the second of
-  which must be less than the fourth. The four points must represent, respectively, the distance
-  from the left edge of the image to the left side of the rectangle, the distance from the top edge
-  to the top side, the distance from the left edge to the right side, and the distance from the top
-  edge to the bottom side, all in <span data-x="'px'">CSS pixels</span>.</p>
+  with exactly four integers, the first of which must be less than or equal to the third, and the
+  second of which must be less than or equal to the fourth. The four points must represent,
+  respectively, the distance from the left edge of the image to the left side of the rectangle, the
+  distance from the top edge to the top side, the distance from the left edge to the right side,
+  and the distance from the top edge to the bottom side, all in
+  <span data-x="'px'">CSS pixels</span>.</p>
 
   <div w-nodev>