tab pane styles/handling mobile/portrait, smaller changes

* tab pane in portrait mode now covers the entire viewport
* tab pane X turned into a chevron
* added divider between tab pane header and content
* changed default tab pane state to open
* added code to scroll messages back to bottom after tab pane animation
  and message input resize

ChatTwo/Http/Frontend/src/components/TabPaneOpener.svelte

@@ -1,7 +1,8 @@
 <script lang="ts">
-    import { tabPaneState, openTabPane } from "$lib/shared.svelte";
+    import { tabPaneState, tabPaneAnimationState, openTabPane } from "$lib/shared.svelte";
 
     function onclick() {
+        tabPaneAnimationState.noAnimation = false;
         openTabPane();
     }
 </script>