Add DB index

Compliments #6555

SQL/tgstation_schema.sql

@@ -202,6 +202,11 @@ CREATE TABLE `library` (
   PRIMARY KEY (`id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
 
+--
+-- Create an index to speed up the libary
+--
+CREATE INDEX deleted_idx ON `library` (`deleted`);
+
 --
 -- Table structure for table `player`
 --