Use 'now visible algorithm' for the PAGE-VISIBILITY hook.
Specify that "orientation lock" is an unordered set.

See #66.
Merge pull request #78 from mounirlamouri/now_visible

Use 'now visible algorithm' for the PAGE-VISIBILITY hook.
Add "participate" block

This PR proposes the ED (as well as any subsequent publication at w3.org/TR/) include a "Participate" block in the spec's boilerplate and that data includes links to the GH repo, Issues, mail list, etc.
Remove SOTD customization.

The "Participate" section already lists all the links.