Add search attribute to search by reference

app/Core/Lexer.php

@@ -33,6 +33,8 @@ class Lexer
         "/^(category:)/"                                 => 'T_CATEGORY',
         "/^(column:)/"                                   => 'T_COLUMN',
         "/^(project:)/"                                  => 'T_PROJECT',
+        "/^(ref:)/"                                      => 'T_REFERENCE',
+        "/^(reference:)/"                                => 'T_REFERENCE',
         "/^(\s+)/"                                       => 'T_WHITESPACE',
         '/^([<=>]{0,2}[0-9]{4}-[0-9]{2}-[0-9]{2})/'      => 'T_DATE',
         '/^(yesterday|tomorrow|today)/'                  => 'T_DATE',
@@ -124,6 +126,7 @@ class Lexer
                 case 'T_STATUS':
                 case 'T_DUE':
                 case 'T_DESCRIPTION':
+                case 'T_REFERENCE':
                     $next = next($tokens);
 
                     if ($next !== false && ($next['token'] === 'T_DATE' || $next['token'] === 'T_STRING')) {