Jan Rehders <jan@sheijk.net> writes:

> Hello,
>
> I’d like to offer my package hideshowvis to be included in nongnu
> elpa. 

Are you sure you don't want the package to be added to GNU ELPA?

>       It has a few users since many years and since Melpa removed
> Emacs wiki packages years ago there has not been a trivial way to
> install it

Here are a few comments and suggestions from looking at the code: