Try to phase out GitHub packages list (or give it lesser priority)

[xTrayambak]

See: #1149

GitHub likes to time-out on many ISPs, and if they don't, ISPs like to poke their nose into it. Reliance Jio in India shadow-bans https://raw.githubusercontent.com because "it helps distribute pirated content" and despite a ton of people complaining to them, they just ignore us (they're a big media giant here, so that make sense).

There's a circumvention by using something like Cloudflare WARP or another VPN. I'd say that we should either phase out the GitHub package list and just run a job on the Nim website server that periodically updates the packages list from the GitHub one (like it currently does!) and remove the GitHub link as a lot of people, including me, have to wait for the GitHub link to time-out, then Nimble advances onto the Nim website mirror. If you CTRL+C during any of that, you end up with what's happening in issue #1149. Or, we can also keep the GitHub link as a fallback in case the Nim website mirror goes down for some reason.

Thoughts?

[penguinite]

Amazing suggestion

I personally think its a great idea to use the nim website mirror first for the reasons you have outlined and then the github mirror as a fallback. But it would be best if we had a non-github mirror as a fallback instead (because of the reasons you have listed)

We could actually have two different mirrors hosted on the same domain, so, main.example.com redirects to the main mirror whilst backup.example.com could redirect to a backup VPS.