Show ellipsis on long file names (#75)

Fixes #69

src/sass/components/_message_media.scss

@@ -148,6 +148,8 @@ $loading-ring-thickness: 5px;
                 line-height: normal;
                 padding: 0;
                 font-size: 10pt;
+                text-overflow: ellipsis;
+                overflow: hidden;
             }
 
             p:first-child {