[css-overscroll-1] Add an overscroll-behavior value which disables local boundary default actions

[vmpstr]

Currently there are 3 overscroll-behavior values:

• auto - which allows chaining, local and non-local boundary default actions
• contain - which allows local boundary default actions, but disallows chaining and non-local boundary default actions
• none - which disallows chaining, local and non-local boundary default actions

It would be nice to also have a value that

1. allows chaining and non-local boundary default actions
2. disallows local boundary default actions.

This would be a nice effect (or lack thereof) when bringing a side menu that shouldn't overscroll and reveal the background, but still allow scroll chaining:
e.g. https://overscroll-menu-vmpstr.yoyo.codes/

from Safari (but similar behavior on FF and Chrome Canary):

I don't have any specific suggestions for the name, but maybe something like forward or continue as a somewhat contrived opposite of contain

@flackr

[flackr]

Or skip as in skip its own local actions but still continue to ancestors...