Add support for custom emojis

Closes #14

DiscordChatExporter/Resources/ExportService/DarkTheme.css

@@ -116,4 +116,10 @@ div.msg-attachment {
 img.msg-attachment {
     max-height: 500px;
     max-width: 50%;
+}
+
+img.emoji {
+    height: 24px;
+    width: 24px;
+    vertical-align: -.4em;
 }

DiscordChatExporter/Resources/ExportService/LightTheme.css

@@ -114,4 +114,10 @@ div.msg-attachment {
 img.msg-attachment {
     max-height: 500px;
     max-width: 50%;
+}
+
+img.emoji {
+    height: 24px;
+    width: 24px;
+    vertical-align: -.4em;
 }

DiscordChatExporter/Services/ExportService.cs

@@ -248,6 +248,10 @@ namespace DiscordChatExporter.Services
             // New lines
             content = content.Replace("\n", "<br />");
 
+            // Custom emojis (<:name:id>)
+            content = Regex.Replace(content, "&lt;:.*?:(\\d+)&gt;",
+                "<img class=\"emoji\" src=\"https://cdn.discordapp.com/emojis/$1.png\" />");
+
             return content;
         }
     }