[resize-observer] Clarify external spec integrations

[johannesodland]

The Intersection Observer specification has a section on External Spec Integrations that makes the integration with the HTML Event Loops Processing Model clear.

I have not been able to find a similar reference in the Resize Observer specification.

Should a similar section be added to the Resize Observer specification, to make it clear that the algorithms are called during the HTML event loop?

[johannesodland]

Hope it’s ok that I tag you here, @Loirooriol and @emilio

[emilio]

I mean, I think the only reason that's the case in intersection observer is because it used to be a monkey-patch... But sure I guess a note mentioning it's used from the HTML event loop is fine? I'd take such a PR unless Oriol objects :)

[Loirooriol]

Sounds ok to me

[johannesodland]

I mean, I think the only reason that's the case in intersection observer is because it used to be a monkey-patch... But sure I guess a note mentioning it's used from the HTML event loop is fine? I'd take such a PR unless Oriol objects :)

I've attempted to add a note in #10512.