Provide Microsoft.AspNetCore.Owin package README (dotnet#57816)

Author: MackinnonBuck

src/Http/Owin/src/PACKAGE.md

@@ -0,0 +1,49 @@
+## About
+
+`Microsoft.AspNetCore.Owin` provides adapters for running OWIN middleware in an ASP.NET Core application, and to run ASP.NET Core middleware in an OWIN application.
+
+## How to Use
+
+To use `Microsoft.AspNetCore.Owin`, follow these steps:
+
+### Installation
+
+```shell
+dotnet add package Microsoft.AspNetCore.Owin
+```
+
+### Configuration
+
+To use OWIN middleware in an ASP.NET Core pipeline:
+1. Define the OWIN middleware, if not done already. Here's a basic "Hello World" example:
+    ```csharp
+    public Task OwinHello(IDictionary<string, object> environment)
+    {
+        var responseText = "Hello World via OWIN";
+        var responseBytes = Encoding.UTF8.GetBytes(responseText);
+
+        // OWIN Environment Keys: https://owin.org/spec/spec/owin-1.0.0.html
+        var responseStream = (Stream)environment["owin.ResponseBody"];
+        var responseHeaders = (IDictionary<string, string[]>)environment["owin.ResponseHeaders"];
+
+        responseHeaders["Content-Length"] = [responseBytes.Length.ToString(CultureInfo.InvariantCulture)];
+        responseHeaders["Content-Type"] = ["text/plain"];
+
+        return responseStream.WriteAsync(responseBytes, 0, responseBytes.Length);
+    }
+    ```
+2. Add the middleware to the ASP.NET Core pipeline with the `UseOwin` extension method. For example:
+    ```csharp
+    app.UseOwin(pipeline =>
+    {
+        pipeline(next => OwinHello);
+    });
+    ```
+
+## Additional Documentation
+
+For additional documentation, including examples on running ASP.NET Core on an OWIN-based server, refer to the [official documentation](https://learn.microsoft.com/aspnet/core/fundamentals/owin) on OWIN with ASP.NET Core.
+
+## Feedback &amp; Contributing
+
+`Microsoft.AspNetCore.Owin` is released as open-source under the [MIT license](https://licenses.nuget.org/MIT). Bug reports and contributions are welcome at [the GitHub repository](https://github.com/dotnet/aspnetcore).