Clarify status of Web Components standard (#1795)

Author: TimvdLippe

src/v2/guide/index.md

@@ -387,7 +387,7 @@ In a large application, it is necessary to divide the whole app into components
 
 You may have noticed that Vue components are very similar to **Custom Elements**, which are part of the [Web Components Spec](https://www.w3.org/wiki/WebComponents/). That's because Vue's component syntax is loosely modeled after the spec. For example, Vue components implement the [Slot API](https://github.com/w3c/webcomponents/blob/gh-pages/proposals/Slots-Proposal.md) and the `is` special attribute. However, there are a few key differences:
 
-1. The Web Components Spec is still in draft status, and is not natively implemented in every browser. In comparison, Vue components don't require any polyfills and work consistently in all supported browsers (IE9 and above). When needed, Vue components can also be wrapped inside a native custom element.
+1. The Web Components Spec has been finalized, but is not natively implemented in every browser. Safari 10.1+, Chrome 54+ and Firefox 63+ natively support web components. In comparison, Vue components don't require any polyfills and work consistently in all supported browsers (IE9 and above). When needed, Vue components can also be wrapped inside a native custom element.
 
 2. Vue components provide important features that are not available in plain custom elements, most notably cross-component data flow, custom event communication and build tool integrations.