Can upload new custom emojies

lib/utils/input_utils.dart

@@ -31,3 +31,7 @@ bool validateUrl(String url) {
 /// Validate directory reference
 bool validateDirectoryReference(String ref) =>
     RegExp(r'@[a-zA-Z0-9]+').hasMatch(ref);
+
+/// Validated a shortcut
+bool validateShortcut(String shortcut) =>
+    RegExp(r'^:[a-zA-Z0-9]+:$').hasMatch(shortcut);