Provide Microsoft.Authentication.WebAssembly.Msal package README (#57818)

Author: MackinnonBuck

src/Components/WebAssembly/Authentication.Msal/src/PACKAGE.md

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+## About
+
+`Microsoft.Authentication.WebAssembly.Msal` provides client-side authentication using Microsoft Authentication Library (MSAL) for Blazor apps running under WebAssembly.
+
+## How to Use
+
+To use `Microsoft.Authentication.WebAssembly.Msal`, follow these steps:
+
+### Installation
+
+```shell
+dotnet add package Microsoft.Authentication.WebAssembly.Msal
+```
+
+### Usage
+
+For usage examples and documentation, refer to the [offical documentation](https://learn.microsoft.com/aspnet/core/blazor/security/webassembly) on Blazor WebAssembly security and identity.
+
+## Feedback & Contributing
+
+`Microsoft.Authentication.WebAssembly.Msal` 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).