feat(ts): add microdata meta tag type (#382)

* Adding schema.org meta tag type

* Changing naming

Author: georgeboot

types/vue-meta.d.ts

@@ -62,6 +62,12 @@ export interface MetaPropertyName extends MetaDataProperty {
   template?: (chunk: string) => string
 }
 
+export interface MetaPropertyMicrodata extends MetaDataProperty {
+  itemprop: string,
+  content: string,
+  template?: (chunk: string) => string
+}
+
 // non-w3c interface
 export interface MetaPropertyProperty extends MetaDataProperty {
   property: string,
@@ -123,7 +129,7 @@ export interface MetaInfo {
     href: string
   }
 
-  meta?: (MetaPropertyCharset | MetaPropertyEquiv | MetaPropertyName | MetaPropertyProperty)[]
+  meta?: (MetaPropertyCharset | MetaPropertyEquiv | MetaPropertyName | MetaPropertyMicrodata | MetaPropertyProperty)[]
   link?: LinkProperty[]
   style?: StyleProperty[]
   script?: (ScriptPropertyText | ScriptPropertySrc)[]