[web-animations-2] Use dfn type for animation trigger values

[tidoust]

The values for "animation trigger state" and "animation trigger type" were defined with a value definition type. That type is reserved for CSS values: https://speced.github.io/bikeshed/#dfn-types

This makes tools that crawl specs to extract machine-readable information wrongly assume that the spec introduces new CSS values.

There is no specific definition type available for generic values. This update uses a regular dfn and updates references to these values accordingly.

[ydaniv]

Thanks for opening this PR! Regarding state, I think correct the dfn to a simple one and not value was the thing I was missing, good catch!
Regarding type, it's actually a value: https://drafts.csswg.org/css-animations-2/#animation-trigger-type
So these should probably remain as values?

[tidoust]

Regarding type, it's actually a value: https://drafts.csswg.org/css-animations-2/#animation-trigger-type
So these should probably remain as values?

Ah, sorry, I had missed that, indeed! There should be only one normative definition of anything, so if css-animations-2 defines the values, web-animations-2 should reference them and not attempt to re-define them. I pushed a new commit that replaces the <dfn> tags with references to the values in css-animations-2.

[ydaniv]

@tidoust thanks! LGTM.

so if css-animations-2 defines the values, web-animations-2 should reference them and not attempt to re-define them.

In css-animations-2 we have a more user-facing definition which describes the behavior of each type for authors.
In web-animations-2 we have a more implementor-facing definition which describes the behavior of each type for implementors.
See @flackr's comment here.