Add an example of using UnscopedRefAttribute to fix CS8170

docs/csharp/language-reference/compiler-messages/cs8170.md

@@ -35,7 +35,7 @@ public class Other
     public void Method()
     {
         var p = new Program();
-        var d = p.M();
+        ref int d = ref p.M();
     }
 }
 ```
@@ -83,3 +83,31 @@ public class Other
     }
 }
 ```
+
+Another approach is to use the <xref:System.Diagnostics.CodeAnalysis.UnscopedRefAttribute?displayProperty=nameWithType> attribute. It will mark the reference to be allowed to escape the scope.<br/>
+Use this only when you know that it is safe for the reference to leave the scope.
+Below is the example of applying <xref:System.Diagnostics.CodeAnalysis.UnscopedRefAttribute?displayProperty=nameWithType> to `int M()` method, which fixes the CS8170:
+
+```csharp
+using System.Diagnostics.CodeAnalysis;
+
+struct Program
+{
+    public int d;
+
+    [UnscopedRef]
+    public ref int M()
+    {
+        return ref d;    // No error - ref is valid to escape the scope in this line of that method
+    }
+}
+
+public class Other
+{
+    public void Method()
+    {
+        var p = new Program();
+        ref int d = ref p.M();
+    }
+}
+```