SerializedDictonary - Add Implicit/Explicit Cast from Dictonary to SerializedDictonary

[AJulliard]

When having

var myDictonary = new Dictonary<>();

And if we want to cast to SerializedDictonary, either (SerializedDictonary)myDictonary and myDictonary as SerializedDictonary work. It could be usefull to be able to do it :)