update hero image alt text

src/components/VizTitle.vue

@@ -31,7 +31,7 @@
                 (min-width: 1201px) 1280px, 
                 1920px"
           src="@/assets/images/responsive_images/hero_no-faces_5-1280.jpg"
-          alt="Social vulnerability and water insecurity"
+          alt="Two contrasting images of water sources with the left image shows a close-up of a hand holding a clear glass being filled with water from a kitchen faucet. The right image shows a rustic landscape with a blue well tank labeled WELL-X-TROL with a fire fence and dry grass in the background."
           @load="onImageLoad"
         />
       </picture>
@@ -50,7 +50,7 @@
               (min-width: 1201px) 1280px, 
               1920px"
         src="@/assets/images/responsive_images/hero_no-faces_5-1280.jpg"
-        alt="Social vulnerability and water insecurity (grayscale)"
+        alt="Two contrasting grayscale images of water sources with the left image shows a close-up of a hand holding a glass being filled with water from a kitchen faucet. The right image shows a rustic landscape with a  well tank labeled WELL-X-TROL with a fire fence and dry grass in the background."
       />
       <picture>
         <!-- Serve WebP images  -->