`<area>` with no `coords` attribute should be an error when `shape` attribute with `circle`, `poly`, or `rect` value is present
For example, given this HTML:
<map name="foo"><area shape="circle"></map> <map name="bar"><area shape="poly"></map> <map name="baz"><area shape="rect"></map>
HTML-Validate does not consider it errors but should do so as per the spec:
In the circle state, area elements must have a coords attribute present, with three integers, the last of which must be non-negative.
In the polygon state, area elements must have a coords attribute with at least six integers, and the number of integers must be even.
In the rectangle state, area elements must have a coords 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.
Note that omitted/invalid
shape attribute value will fallback to the
The attribute may be omitted. The missing value default and invalid value default are the rectangle state.