[HTML] Improve how the reference symbol looks

Closes #650

DiscordChatExporter.Core/Exporting/Writers/Html/PreambleTemplate.cshtml

@@ -206,17 +206,15 @@
 
         .chatlog__reference-symbol {
             grid-column: 1;
+            margin: 8px 4px 4px 18px;
             border-left: 2px solid @Themed("#4f545c", "#c7ccd1");
             border-top: 2px solid @Themed("#4f545c", "#c7ccd1");
             border-radius: 8px 0 0 0;
-            margin-left: 16px;
-            margin-top: 8px;
         }
 
         .chatlog__reference {
             display: flex;
             grid-column: 2;
-            margin-left: 1.2em;
             margin-bottom: 0.25em;
             font-size: 0.875em;
             white-space: nowrap;
@@ -275,6 +273,7 @@
             grid-column: 1;
             width: 40px;
             height: 40px;
+            margin-right: 16px;
         }
 
         .chatlog__author-avatar {
@@ -285,7 +284,6 @@
 
         .chatlog__messages {
             grid-column: 2;
-            margin-left: 1.2em;
             min-width: 50%;
         }