ENGCOM-3932: #18347 - Element 'css', attribute 'as': The attribute 'a…

…s' is not allowed. (CSS preloading) #20495

 - Merge Pull Request #20495 from vasilii-b/magento2:2.3-framework-view-element-css-attribute-as
 - Merged commits:
   1. 57f6957

lib/internal/Magento/Framework/View/Layout/etc/head.xsd

@@ -20,6 +20,15 @@
         <xs:attribute name="type" type="xs:string"/>
         <xs:attribute name="order" type="xs:integer"/>
         <xs:attribute name="src_type" type="xs:string"/>
+        <xs:attribute name="as">
+            <xs:simpleType>
+                <xs:restriction base="xs:string">
+                    <xs:enumeration value="font" />
+                    <xs:enumeration value="script" />
+                    <xs:enumeration value="style" />
+                </xs:restriction>
+            </xs:simpleType>
+        </xs:attribute>
     </xs:complexType>
 
     <xs:complexType name="metaType">