Add link to the explainer for legal effects details

[AramZS]

In order to address concerns about updated to the legal effects and remove concerns about delays stemming from WG workflows that might be involved with future modification we aim to address updates to legal effects in the explainer and link to it within the specification. This hopefully will address #53

[chrisn]

I suggest going further and moving the entire section to the explainer. As the original issue discussed, legal frameworks are a moving target and so will be easier to maintain separately, including for those current described in the spec.

[SebastianZimmeck]

I suggest going further and moving the entire section to the explainer. As the original issue discussed, legal frameworks are a moving target and so will be easier to maintain separately, including for those current described in the spec.

Good point, @chrisn. Since a number of people expressed this preference, that is what we are going to do, i.e., move the legal details to the explainer, keep some general remarks in the spec itself, and (non-normatively) link to the explainer from the spec.

I'll merge these changes now so that we have a clean slate to make these changes in the spec and explainer.