Improvements to site performance & accessibility

Added alt tags, language, and defered loading to assets that are not needed immediately.

site.webmanifest

@@ -13,7 +13,8 @@
             "type": "image/png"
         }
     ],
-    "theme_color": "#ffffff",
-    "background_color": "#ffffff",
+    "start_url": "/",
+    "theme_color": "#CCFF00",
+    "background_color": "#CCFF00",
     "display": "standalone"
 }