Make List Count function const.

src/Collections/List.hpp

@@ -48,7 +48,7 @@ namespace Arbutils::Collections {
         inline ValueT& operator[](size_t index) { return At(index); }
         inline const ValueT& operator[](size_t index) const { return At(index); }
 
-        inline size_t Count() { return _vector.size(); }
+        inline size_t Count() const { return _vector.size(); }
 
         iterator begin() { return _vector.begin(); }
         iterator begin() const { return _vector.begin(); }