Add img|creative height & width attribute

This will help reserver the correct space for the given creative/ad and helps prevent issues with cls  & lighthouse scoring.

packages/marko-web-mindful-ads/components/render.marko

@@ -17,7 +17,7 @@ $ /** @type {import("../utils/fetch-ads").MindfulWebsiteBannerCreative} **/
     data-unit-id=unit._id
   >
     <a href=creative.clickUrl target="_blank">
-      <img src=creative.src alt=creative.name />
+      <img src=creative.src alt=creative.name height=creative.height width=creative.width />
     </a>
   </div>
 </for>