Expose underlying mobile support from winit via cfg changes

[markkimsal]

I understand mobile support is not a priority, and possibly even a detriment if it attracts more spurious bug reports. But, with just 6 lines of code changes iced can expose underling winit android support. This goes a long way to closing #302 with no ongoing maintenance from iced core team.

4 lines are cfg changes that more closely align with the underlying winit library

--- a/winit/src/conversion.rs
+++ b/winit/src/conversion.rs
@@ -203,13 +203,25 @@ pub fn window_event(
         WindowEvent::KeyboardInput { is_synthetic, .. } if is_synthetic => None,
         WindowEvent::KeyboardInput { event, .. } => Some(Event::Keyboard({
             let key = {
-                #[cfg(not(target_arch = "wasm32"))]
+                #[cfg(any(
+                    target_os="windows",
+                    target_os="macos",
+                    all(feature = "x11", all(unix, not(any(target_os = "ios", target_os = "macos")), not(target_os = "android"), not(target_os = "emscripten")), not(target_os = "redox")),
+                    all(feature = "wayland", all(unix, not(any(target_os = "ios", target_os = "macos")), not(target_os = "android"), not(target_os = "emscripten")), not(target_os = "redox")),
+                    target_os="redox",
+                ))]

Checking only for wasm32 let's unsupported platforms slip through the feature gate of KeyEventExtModifierSupplement, because the underlying core winit library uses a different set of platform checks.

This will allow more platform support transparently by matching the cfg of the underlying winit library.

winit 0.31 plans to remove config aliases in favor of raw cfg macros. rust-windowing/winit#3539

Lastly, re-exporting 2 winit features into the iced_winit workspace Cargo allows the underlying winit + android-activity to build when targeting aarch64-linux-android

--- a/winit/Cargo.toml
+++ b/winit/Cargo.toml
@@ -22,6 +22,8 @@ x11 = ["winit/x11"]
 wayland = ["winit/wayland"]
 wayland-dlopen = ["winit/wayland-dlopen"]
 wayland-csd-adwaita = ["winit/wayland-csd-adwaita"]
+android-native-activity = ["winit/android-native-activity"]
+android-game-activity = ["winit/android-game-activity"]
 unconditional-rendering = []

There are all the changes to allow successful building on android - fonts don't work, but that is another small pr.