Restore SVGSVGElement.prototype.getElementById #182
Description
It was removed in 3d61d59
The Chromium issue and use counter:
https://bugs.chromium.org/p/chromium/issues/detail?id=313655 (when filed the DOM spec had it on ParentNode, now it's on NonElementParentNode)
https://www.chromestatus.com/metrics/feature/timeline/popularity/778
Usage is high enough that it doesn't seem worth inconveniencing anyone for this, given current support, see comments on the linked removal commit.