doc: is exporting a class the same as the constructor

[JosiahParry]

Related #348

The package website says:

"If you export a class, you must also set the package argument, ensuring that classes with the same name are disambiguated across packages."

What I am not clear of here is if exporting a class is the same as exporting the constructor. Is this the case?

I think a super simple code example with #' @export in this section would do wonders to clarify that.

Additionally, in this context, is there a naming convention we should follow for the class constructors? (I could make a new issue for this if desired)