gpui: Add support for observing window appearance (#7294)
This PR adds support to GPUI for observing when the appearance of a
window changes.
Based on the initial work done in
https://github.com/zed-industries/zed/pull/6881.
Release Notes:
- N/A
115f0672fbMarshall Bowers committed on 2/2/2024, 6:13:35 PM· committed by GitHubparent1f6bd67