gpc-spec support resource

We had a good discussion Wednesday on the GPC support resource. Justin
provides an overview
<https://github.com/privacycg/gpc-spec/issues/33#issuecomment-1442527181>
and Pete a PR <https://github.com/privacycg/gpc-spec/pull/48>. If anyone
has comments, please feel free to chime in.

Best regards,

Sebastian

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We launched Global Privacy Control <https://globalprivacycontrol.org/>
privacy-tech-lab <https://www.privacytechlab.org/>, Wesleyan University