title: Get the size of std::any
body: <p>Is there any way to get the size (in bytes) of the data stored by <code>std::any</code>? The only workaround I came up with is querying the type of its value by <code>std::any::type</code> and comparing the result to a list of known types like <code>my_any.type() == typeid(T)</code>, then the size is <code>sizeof(T)</code>. Unfortunately, this solution only works when the types are known beforehand.</p>
  
  <p>Do you know any solution?</p>