Add WeakReference<T> to sandbox

RELEASE-NOTES.md

@@ -40,6 +40,7 @@ END TEMPLATE-->
 ### New features
 
 * `Control.OrderedChildCollection` (gotten from `.Children`) now implements `IReadOnlyList<Control>`, allowing it to be indexed directly.
+* `System.WeakReference<T>` is now available in the sandbox.
 
 ### Bugfixes
 

Robust.Shared/ContentPack/Sandbox.yml

@@ -1560,6 +1560,11 @@ Types:
     ValueType: { All: True }
     Version: { All: True }
     Void: { All: True }
+    WeakReference`1:
+      Methods:
+      - "void .ctor(!0)"
+      - "bool TryGetTarget(ref !0)"
+      - "void SetTarget(!0)"
   YamlDotNet.Core.Events:
     MappingStyle: { } # Enum
     SequenceStyle: { } # Enum