[css-text-4] Specify width of autospace gaps

[fantasai]

@r12a wrote:

There appears to be no way to set the width of the gap introduced by autospace. That turned out to be something that content authors had different opinions about, or may use different widths in different contexts.

Note this has been brought up a few times over the years. We might not introduce such controls in the first level, but we should be prepared to do something about it in the future.

As far as I'm aware, the main request is for control over inter-script spacing (not over, e.g. punctuation spacing, which at least in French is fairly standardized). I suspect we can have one point of control for both ideograph-alpha and ideograph-numeric. Would be good to confirm.

[fantasai]

Note @MurakamiShinyu's proposal in #6950 (comment)

Another possibility would be to add a third longhand to the set proposed in #4246 (comment)

[xfq]

I suspect we can have one point of control for both ideograph-alpha and ideograph-numeric. Would be good to confirm.

We discussed this in yesterday's CLReq Editors' Call and concluded that we can have one point of control for both ideograph-alpha and ideograph-numeric. We didn't find a use case to control them separately.