Implementation status: consider specific icon for "origin trials"

[tidoust]

Experimental implementations of an API may be restricted to an allow list of origins. That seems worth pointing out, since it means that the API is not yet available to everyone but requires some kind of registration.

Chrome Platform Status reports such features through an origintrial boolean flag. This flag could trigger the appearance of a "origin trial" icon.

Note that we already have a "requires a prefix" icon, and "behind a flag" icon. In theory, all 3 icons could have to be rendered at once, but in the interest of keeping the status readable, we should probably just render the "origin trial" icon when appropriate, and not bother with the other ones.

[tidoust]

Two current examples of specs under origin trials:

• The Badging API: https://www.chromestatus.com/feature/6068482055602176
• User Idle Detection: https://www.chromestatus.com/feature/4590256452009984