Yet another SwiftUI clone, other interesting developments

Earlier I had mentioned OpenSwiftUI 
<https://github.com/OpenSwiftUIProject/OpenSwiftUI>, a free 
reimplementation of SwiftUI that we might be able to use if we ever 
implement the Swift-ObjectiveC bridge and implement CAAppKitBridge.

Here's a few other interesting developments in the Swift world.

There's SwiftCrossUI <https://github.com/stackotter/swift-cross-ui>, 
which seems to have a lot more platform support than OpenSwiftUI. It 
currently has AppKit, UIKit, WinUI, Gtk4, and Gtk3 backends. It diverges 
from SwiftUI in some aspects, in order to make it easier to keep being 
cross-platform.

@JWIMaster <https://github.com/JWIMaster> has built a Swift 5.10 
toolchain for iOS 6 
<https://github.com/JWIMaster/Swift-5.10.1-for-iOS-6>, along with 
polyfills for UIKit <https://github.com/JWIMaster/UIKitCompatKit> and 
Foundation <https://github.com/JWIMaster/FoundationCompatKit>. They have 
started on implementing support for iOS 6 in SwiftCrossUI 
<https://github.com/stackotter/swift-cross-ui/issues/216>.

Skip <https://skip.tools/> is an implementation of SwiftUI for Android 
on top of Jetpack Compose (the current Google-recommended UI library for 
Android). It also has an interesting build tool (proprietary), which 
deals with Swift-JVM bridging and also is able to transpile Swift to 
Kotlin, or do a native (i.e. via the Swift LLVM compiler) build of the 
Swift code.

SwifDroid <https://github.com/swifdroid> tries to do it a bit 
differently, by having a SwiftUI-like UI framework which is modified 
specifically to match the Android-native models of app lifecycle and UI. 
It has its own Swift-JVM bridge (different from Skip's), and does not 
have any proprietary components.

All in all, there's a lot of interesting developments going on in the 
cross-platform Swift sphere. These are probably not directly relevant, 
but once we implement the Swift-ObjectiveC bridge they may become pretty 
useful, as it can give us access to Android's native UI framework, and 
we can use OpenSwiftUI or SwiftCrossUI to provide a SwiftUI frontend on 
top of gnustep-gui.