Unable to document `@data`

[Carlos Parada]

As in the title, it's not currently possible to document Structs created using the @data macro; adding a docstring above them results in an error. (You can attach the docstring further down, but that makes the code a bit harder to read.)

Relatedly, the current naming of ADTs as x's constructor makes it a bit harder to document them. Could you explain what's going on with them?