Preload HSTS for `nushell.sh`

[lgarron]

https://hstspreload.org/ is using HTTPS, but is not using the full protection of HSTS preloading:

• https://scotthelme.co.uk/hsts-the-missing-link-in-tls/?ref=scotthelme.co.uk
• https://scotthelme.co.uk/hsts-preloading/

If the subdomains are not used for any private infrastructure I would recommend using the following header:

Strict-Transport-Security: max-age=63072000; includeSubDomains; preload

The site seems to be hosted with GitHub Pages. If you'd like to set this header there's no UI for it in GitHub (yet), but I believe @yoannchaudet should be able to enable it.

[yoannchaudet]

We handle these requests via the support. Don't hesitate to open a ticket https://support.github.com/contact.