Update link to GitHub pages

[splorp]

The link located in the “About” sidebar which points at the documentation published via GitHub Pages is incorrect for this repo.

GitHub deprecated subdomains of github.com as of April 2021.

The link should be changed from Gnue’s original link:

https://gnue.github.com/NEWT0

To the current link in this fork:

https://matthiaswm.github.io/NEWT64

Or to the current link in the original repo:

https://gnue.github.io/NEWT0

Thanks!