Explain how this is related to the Foldables proposal

[tomayac]

Should this somewhere explain how it's related to Foldables? The Edge explainer references this present explainer.

[kenchris]

@diekus fyi

The link to that spec work can be found here: https://w3c.github.io/screen-fold/

[plinss]

A concern that was raised in a TAG meeting (see w3ctag/design-reviews#413) is that the foldables work is still in flux and this API needs to blend seamlessly with that work. If these APIs don't ship in lock-step there is a risk that one will ship, the ongoing work in the other will then require changes, but the shipping API will not be able to change due to web compat issues.

[michaelwasserman]

We have been coordinating with Screen Fold (Device Posture) and Window Segment proposals through the Second Screen Community Group. While hardware and paradigms are indeed evolving, there is a fairly stable problem space where we can align complimentary proposals. The CG even produced a Form Factors draft report with some guiding principles for using these APIs.

This repo's explainer and readme point to the other proposals and the report. We're continually aligning to avoid compatibility issues, but any specific issues should definitely be raised, like here and here.