[pointer-animations] Minor syntax suggestions

[cdoublev]

is already defined in Scroll Animations, which is a problem for CSS tools like w3c/webref and its users (like MDN). Not sure what is the best solution. Perhaps it could be defined in CSS Logical. At worst, it should be defined only once.

expands to the same keywords than in Scroll Animations. Besides, "source" seems a bit general, which could prevent using this production name with other values in other contexts. Perhaps both could be replaced with or whatever production name would be appropriate?

[AtkinsSJ]

I noticed this is already partly addressed in #12283. cc @tidoust

[ydaniv]

Thanks @cdoublev! I approved #12283 which addresses both.
Ideally could probably be reused for both SDA and PDA.
And should be prefixed, like in the PR above.

[cdoublev]

Alright. The main issue was the duplication of definitions. So closing as fixed by #12283 then.

Two other suggestions though...

could be used in the value definition of *-timeline-axis.

animation-range-center is defined with below its definition table. I guess it should be , like in the definition table.