[webcomponents] Migrate the bugs filed for Custom Elements from bugzilla to GitHub Issues, here. (#119)

It would be better to migrate the custom elements bugs from bugzilla [1] into here, as the bugs for Shadow DOM were done, for the consistency.
[1] https://www.w3.org/Bugs/Public/showdependencytree.cgi?id=14968&hide_resolved=1

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/119