Shadow DOM spec bugs will be migrated into GitHub issues

Regarding with the Shadow DOM spec, more and more workflows are happening
[1] on GitHub w3c/webcomponents repository recently.
Therefore, I am thinking about migrating the bugs of the Shadow DOM spec,
from the bugzilla [2], to the GitHub issues [3], as some of other specs are
already doing so.

As an experiment, I've just migrated the existing open bugs on the bugzilla
to the GitHub issues, by a tiny script I've written using GitHub APIs.

Unless there is an objection to the migration, I am going to close the
existing open Shadow DOM spec bugs on the bugzilla, with a link to the
corresponding bug on the GitHub issues.

Please let me know if you have a concern.

[1] https://github.com/w3c/webcomponents/commits/gh-pages
[2] https://www.w3.org/Bugs/Public/showdependencytree.cgi?id=14978
[3] https://github.com/w3c/webcomponents/issues