Static Avalonia views for Elmish programs

This project is a port of the awesome Elmish.WPF library. Most of the codebase is directly copied, but the WPF bits have been replaced with Avalonia bits and adapted where necessary. There is a sample project here to get you started, but there is a plethora of Elmish.WPF examples that you can also refer to.

Avalonia.FuncUI already exists and it is fantastic. So then why make an Elmish.Avalonia port?

• Some people may prefer using xaml, and it can be an easier sell for some teams due to the immediate availability of all community controls.
• Bindings have to be created for controls in FuncUI. While most of the controls have bindings provided, some controls (such as the DataGrid) are "too OOP" and are difficult or impossible to create bindings for. This makes a library like Elmish.Avalonia very useful as it sidesteps this problem altogether by using xaml.
• There is not currently a reliable design preview tool for FuncUI (there is a very experimental project, but the author has stopped working on it and it's way too complex for me to want to mess with it). For me to do any kind of real project work with Avalonia and F#, a design preview is a necessity, and using xaml allows you to utilize the custom Avalonia design preview extension. After recently trying Elmish.WPF, I fell in love with the ViewModel.designInstance preview functionality that lets you preview your init values in the design preview panel, and this also works with Elmish.Avalonia!
• You can use Avalonia.FuncUI and Elmish.Avalonia side-by-side to have the best of both worlds!

• Avalonia UI is a big deal in the .NET OSS community; it is always nice for F# community to be able to participate in the latest and greatest with as many options as possible.
• Avalonia already provides first class templates to create an F# project that include creating .axaml views within the same project! (Not possible with WPF!)
• While the built-in F# templates do allow you to do classic MVVM style, Elmish is more powerful and has become the standard for F# UI projects.
• The "Avalonia UI for Visual Studio 2022" extension provides a xaml preview pane that works with F#! 😄 (Also not possible with WPF!)
• The Elmish.WPF ViewModel.designInstance concept works with this extension very well. This allows you populate your "Design Preview" window with the defaults from your Elmish init function!
• Keeping with tradition that the F# community will provide important libraries, developer tools and workload support.

The included sample app shows a obligatory Elmish counter app, and also the Avalonia DataGrid control.

Don't forget to install the "Avalonia for Visual Studio 2022" extension. JetBrains Rider also supports Avalonia previews out-of-the-box! https://docs.avaloniaui.net/docs/getting-started/ide-support

The sample project uses the ViewLocator to instantiate the view, bind the Elmish view model and start the Elmish loop. Since the design preview is set for both the MasterView and the CounterView, we are able to see the counter on the MasterView design preview!

As of now, the easiest way to get started is to copy the included AvaloniaExample project.

Here are some key differences from the default F# MVVM template in the AvaloniaExample project:

1. The Avalonia.ReactiveUI package has been replaced with the Elmish.Avalonia package.
2. In Program.fs, .UseReactiveUI() has been replaced with .UseElmishBindings().
3. The template ViewLocator has code has been modified to work with a custom IStart that makes it easier to bind the view/viewmodel and start the Elmish loop. This allows us to bind the MainView.axaml Content via the ViewLocator to locate the appropriate view and start the Elmish loop.