[SwiftmailerBundle] Add missing spool type attribute in swiftmailer-1.0.xsd

src/Symfony/Bundle/SwiftmailerBundle/Resources/config/schema/swiftmailer-1.0.xsd

@@ -26,6 +26,7 @@
   </xsd:complexType>
 
   <xsd:complexType name="spool">
+    <xsd:attribute name="type" type="xsd:string" />
     <xsd:attribute name="path" type="xsd:string" />
   </xsd:complexType>