Provide Microsoft.AspNetCore.Authentication.Facebook package README (dotnet#57786)

Author: MackinnonBuck

src/Security/Authentication/Facebook/src/PACKAGE.md

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+## About
+
+`Microsoft.AspNetCore.Authentication.Facebook` provides ASP.NET Core middleware that enables an application to support Facebook's OAuth 2.0 authentication workflow.
+
+## How to Use
+
+To use `Microsoft.AspNetCore.Authentication.Facebook`, follow these steps:
+
+### Installation
+
+```shell
+dotnet add package Microsoft.AspNetCore.Authentication.Facebook
+```
+
+### Configuration
+
+1. Refer to the guide in the official documentation [here](https://learn.microsoft.com/aspnet/core/security/authentication/social/facebook-logins#create-the-app-in-facebook) to create the app in Facebook.
+2. Follow the steps in the official documentation [here](https://learn.microsoft.com/aspnet/core/security/authentication/social/facebook-logins#store-the-facebook-app-id-and-secret) to store the Facebook app ID and secret.
+3. Configure the middleware your ASP.NET Core app's `Program.cs`:
+```csharp
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddAuthentication()
+    .AddFacebook(options =>
+    {
+        options.AppId = Configuration["Authentication:Facebook:AppId"];
+        options.AppSecret = Configuration["Authentication:Facebook:AppSecret"];
+    });
+```
+
+## Main Types
+
+The main types provided by this package are:
+
+* `FacebookOptions`: Represents the options for configuring Facebook authentication
+* `FacebookHandler`: The authentication handler responsible for processing Facebook authentication requests and generating the appropriate authentication ticket
+
+## Additional Documentation
+
+For additional documentation and examples, refer to the [official documentation](https://learn.microsoft.com/aspnet/core/security/authentication/social/facebook-logins) on Facebook login setup in ASP.NET Core.
+
+## Feedback & Contributing
+
+`Microsoft.AspNetCore.Authentication.Facebook` 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).