fix: support once (with skip) client side (fix #498)

src/client/updaters/tag.js

@@ -44,7 +44,10 @@ export default function updateTag (appId, options, type, tags, head, body) {
     }
 
     const newElement = document.createElement(type)
-    newElement.setAttribute(attribute, appId)
+
+    if (!tag.once) {
+      newElement.setAttribute(attribute, appId)
+    }
 
     Object.keys(tag).forEach((attr) => {
       /* istanbul ignore next */

src/shared/constants.js

@@ -104,7 +104,7 @@ export const tagsWithInnerContent = ['noscript', 'script', 'style']
 // Attributes which are inserted as childNodes instead of HTMLAttribute
 export const tagAttributeAsInnerContent = ['innerHTML', 'cssText', 'json']
 
-export const tagProperties = ['once', 'template']
+export const tagProperties = ['once', 'skip', 'template']
 
 // Attributes which should be added with data- prefix
 export const commonDataAttributes = ['body', 'pbody']