web: load the main image on event and news pages eagerly

web/src/components/events/EventHeader.tsx

@@ -49,6 +49,9 @@ export const EventHeader = ({ event }: { event: EventFragment }) => {
             height={featuredImage.height}
             attribution={featuredImage.attribution}
             sizes="(max-width: 1000px) 100vw, 55vw"
+            // the page's largest element, at the top of it
+            loading="eager"
+            fetchPriority="high"
           />
         )}
       </div>

web/src/components/news/NewsPageView.tsx

@@ -59,6 +59,9 @@ export function NewsPageView({ news }: NewsPageViewProps) {
             height={featuredImage.height}
             attribution={featuredImage.attribution}
             sizes="100vw"
+            // the page's largest element, at the top of it
+            loading="eager"
+            fetchPriority="high"
           />
         )}
       </section>