message: docs: add example with empty arrays
diff: @@ -17,7 +17,18 @@ Container Verification
  If a ``Container`` is marked as required (via the ``required()``) method, then the ``Container`` must
  have a ``Field`` or ``Function`` that was present in the input or contain a sub-``Container`` that does.
  -This does not apply to a ``Container`` that corresponds to an array or dictionary.
  +This does not apply to a ``Container`` that corresponds to an array or dictionary, as empty collections
  +provided by the user are considered valid. Consider the following definition and input file:
  +
  +.. code-block:: C++
  +
  + addIntArray("foo").required();
  +
  +.. code-block:: Lua
  +
  + foo = { }
  +
  +Inlet verification will succeed for the above snippets.
  If a ``Container`` corresponds to an array or dictionary, the elements of the array must all be of the requested
  type, if any were provided. This restriction applies even if the array/dictionary was not marked as ``required``.
  