[DOM-Parsing] innerHTML needs special case for <template> (#1)

@nox discovered in https://www.w3.org/Bugs/Public/show_bug.cgi?id=27314#c23 that fragment parsing in HTML does not work correctly. However, it would work correctly if `innerHTML` (and maybe the other APIs too) special case `<template>`. That seems to be the easiest way to address this problem and is how WebKit/Blink implement it reportedly.

Copying @bzbarsky and @hsivonen since they maybe be interested in this as well.

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/DOM-Parsing/issues/1