docs: add link to download site under "Installing modules on ..."

[zerothi]

It is always a little difficult to find the tar.gz for download.
It would be nice if the documentation clearly had links to where to download.

In the top it would be nice with a link to the release pages, for instance.

[cdorbell2]

Hi,
why you don't use the release area under github : https://github.com/cea-hpc/modules/releases

[zerothi]

I do, but for readers of the documentation it makes more sense to have a link to the actual release page.
When I am reading in the docs about "Installation" it would be natural to have a link where to download said files.

[xdelaruelle]

Thanks a lot for this input. Indeed a proper link to a dist archive in the installation documentations is missing (for both Unix and Windows).

[xdelaruelle]

Fixed by 77cc539