Support: template element attributes

[lukejans]

requesting support for attributes that are used on the template element.

<template  shadowrootmode="open" 
           shadowrootclonable
           shadowrootdelegatesfocus>

</template>

This element is used with the shadow DOM for building web-components and contains a document fragment. The shadowrootopen attribute allows you to use declarative shadow DOM which improves load times by reducing javascript code to render the element.

more info on <template> at MDN
more info on html living standard