added set database key hyperlink

Author: Gioee

sqlite-cloud/reference/backup-commands.mdx

@@ -7,7 +7,7 @@ slug: backup-commands
 ---
 
 ## APPLY BACKUP SETTINGS
-Several backup-related settings can be applied using the SET DATABASE KEY command.
+Several backup-related settings can be applied using the [SET DATABASE KEY](https://docs.sqlitecloud.io/docs/settings-commands#set-database-key) command.
 
 The following keys affect the backup settings:
 * **backup**: set to 1 to activate a backup, 0 to disable.