Make EnvironmentObject disposable

Author: TimLariviere

src/Fabulous/Components/EnvironmentObject.fs

@@ -1,5 +1,6 @@
 namespace Fabulous
 
+open System
 open System.Runtime.CompilerServices
 
 type EnvironmentObjectRequest<'T> = delegate of unit -> EnvironmentKey<'T>
@@ -9,6 +10,11 @@ type EnvironmentObject() =
     let changed = Event<unit>()
     member this.Changed = changed.Publish
     member this.NotifyChanged() = changed.Trigger()
+    abstract member Dispose: unit -> unit
+    default this.Dispose() = ()
+
+    interface IDisposable with
+        member this.Dispose() = this.Dispose()
 
 [<AutoOpen>]
 module EnvironmentObjectBuilders =

src/Fabulous/EnvironmentContext.fs

@@ -81,3 +81,9 @@ and [<AllowNullLiteral>] EnvironmentContext(logger: Logger, inheritedContext: En
 
             if valuePropagationSubscription <> null then
                 valuePropagationSubscription.Dispose()
+
+            for value in values.Values do
+                if value :? IDisposable then
+                    (value :?> IDisposable).Dispose()
+
+            values.Clear()