this is clearly something out of our control.
The curl output shows that curl resolves the domain to 0.0.0.0 which is obviously wrong. What confuses me is that curl actually fails when it can’t resolve a domain to an address. So I would check your local DNS client and the configured DNS servers. You can also run
dig @<your-dns-ip-address> raw.githubusercontent.com to see if the resolution works.
And I just notice that this can also be some kind of “security” applied by your network operator so that he prevents access to a set of domains by resolving them to 0.0.0.0. I guess you are in any kind of company or public network?
This is unfortunately we can not really fix and needs to be solved on the client side.