Update README.md about UWP, .NET MAUI, WIN UI 3 (#243)

* Update README.md about UWP .NET MAUI WIN UI 3

* Updated info, and fixed grammar mistakes.

README.md

@@ -146,3 +146,30 @@ dotnet build -c Release
 **Unity3D**
 
 If you wish to have barebones Unity3D implementation, you need to build the `DiscordRPC.dll`, the [Unity Named Pipes](https://github.com/Lachee/unity-named-pipes) Library and the [UnityNamedPipe.cs](https://github.com/Lachee/discord-rpc-csharp/blob/master/Unity%20Example/Assets/Discord%20RPC/Scripts/Control/UnityNamedPipe.cs). Put these in your own Unity Project and the `.dll`s in a folder called `Plugins`. 
+
+**UWP / .NET MAUI / WIN UI 3**
+
+For now, the library doesn't work on UWP applications until we find the issue and fix it.
+
+In order to make this library work with the WIN UI 3 related applications such as .NET MAUI, you need to define `runFullTrust` Capability inside `Package.appxmanifest`.
+
+Here is an example of how to add `runFullTrust` to your WIN UI 3 application:
+
+`Package.appxmanifest`:
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+
+<Package
+  xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10"
+  xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
+  xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
+  IgnorableNamespaces="uap rescap">
+  ...
+    <Capabilities>
+	    <rescap:Capability Name="runFullTrust" />
+    </Capabilities>
+</Package>
+```
+
+If you use .NET MAUI or WIN UI 3 template for C#, it automatically puts `runFullTrust` capability.