[WebIDL] add text to discourage `[Optional] Interface / [NoInterfaceObject] interface Interface` and encourage `dictionary Dictionary` instead

I recently saw a snippet of Web IDL code that goes like this:
  function A(Foo foo, [Optional] Bar bar);

  [NoInterfaceObject] interface Bar
    { ... };

In response to this, I'd like Web IDL to include some text to the effect of:

    You SHOULD use `dictionary Foo` instead of `[NoInterfaceObject]
interface Foo` if Foo is intended for use as an argument, especially
an [Optional] argument.