- add flag images for language switcher

- hide messages if room parameter is not given

assets/uk.svg

@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 60 30">
+  <clipPath id="t">
+    <path d="M30,15 h30 v15 z v15 h-30 z h-30 v-15 z v-15 h30 z"/>
+  </clipPath>
+  <path d="M0,0 v30 h60 v-30 z" fill="#012169"/>
+  <path d="M0,0 L60,30 M60,0 L0,30" stroke="#fff" stroke-width="6"/>
+  <path d="M0,0 L60,30 M60,0 L0,30" clip-path="url(#t)" stroke="#C8102E" stroke-width="4"/>
+  <path d="M30,0 v30 M0,15 h60" stroke="#fff" stroke-width="10"/>
+  <path d="M30,0 v30 M0,15 h60" stroke="#C8102E" stroke-width="6"/>
+</svg>