Support for Back button Key on Android (#7073)

When your press a Back button on Android (for example at
`native-activity`), [Winit translates this
key](47b938dbe7/src/platform_impl/android/keycodes.rs (L237C42-L237C53))
as `NamedKey::BrowserBack`. Added convertion to `Key::Escape` at
`egui-winit` module.

---------

Co-authored-by: Advocat <advocat@ogr.local>

crates/egui-winit/src/lib.rs

@@ -1144,6 +1144,8 @@ fn key_from_named_key(named_key: winit::keyboard::NamedKey) -> Option<egui::Key>
         NamedKey::F33 => Key::F33,
         NamedKey::F34 => Key::F34,
         NamedKey::F35 => Key::F35,
+
+        NamedKey::BrowserBack => Key::BrowserBack,
         _ => {
             log::trace!("Unknown key: {named_key:?}");
             return None;