Spec what it means to support "manifest" via <link>'s relList

[marcoscaceres]

We need to spec out:

document.createElement("link").relList.supports("manifest");

This might actually go into HTML... just putting it here as reminder.

[marcoscaceres]

Noting, browsers:

• Safari: true
• Chrome: true
• Firefox: false - bug https://bugzilla.mozilla.org/show_bug.cgi?id=1596040

[marcoscaceres]

Fixed in Firefox (Fenix will return true - and I think Firefox nightly too, as DevTools now has an "Applications" tab that processes the manifest).

@aarongustafson, this is related #778 ... we should get this "for free" when it goes into HTML, but please double check with the HTML crew when you send the PR to HTML (please cc me too).

[aarongustafson]

Related to #778

[aarongustafson]

I was interested in trying to build a platform test, so I took a stab at it.

[aarongustafson]

@marcoscaceres Is this one clear to close or is there more work to do on this?

[marcoscaceres]

Let's close it... this will now be handled over on the HTML side for free.