Add Delegate class reference

Breathe can't handle `Delegate< ReturnType(ParamTypes...) >`

Sming/Core/Delegate.h

@@ -17,6 +17,10 @@
 #include <functional>
 using namespace std::placeholders;
 
+/**
+ * @brief  Delegate class, encapsulates a std::function
+ * Added constructor template implements lambda callback which is more efficient than std::bind.
+ */
 template <typename> class Delegate; /* undefined */
 
 /** @brief  Delegate class

docs/source/information/events.rst

@@ -91,3 +91,7 @@ This flexibility comes at a cost, however:
 These are the main reasons why you should not use Delegates in an interrupt context.
 
 See :pull-request:`1734` for some further details about the relative speeds.
+
+
+.. doxygenclass:: Delegate
+   :members: