Misc · Web: a web view proven with wry, and an iframe embed

misc::WebView lays wry 0.57's child WKWebView over the window at its
box, following it from a canvas in prepaint and hiding it out of view;
it loads an address or the owner's HTML, which makes it the HTML
preview. misc::IframeEmbed frames a page under its address with Open
in browser. EmbedCard points to chat::LinkPreviewCard, ShareSheet to
buttons::ShareButton; PrintButton is blocked, gpui 0.2.2 has no print
API.

src/misc/mod.rs

@@ -13,6 +13,7 @@ mod survey;
 #[cfg(all(test, feature = "test-support"))]
 mod tests;
 mod units;
+mod web;
 
 pub use calculator::Calculator;
 pub use captcha::{Captcha, CaptchaState};
@@ -27,3 +28,4 @@ pub use scanner::QrCodeScanner;
 pub use stopwatch::Stopwatch;
 pub use survey::{Answer, Question, Survey};
 pub use units::UnitConverter;
+pub use web::{IframeEmbed, WebSource, WebView};