Here's how to access GitHub despite a DNS outage. This tutorial is for Mac, but the general idea applies to other operating systems, too.
1) Adding GitHub to your hosts file
First, Get the A records for
assets-cdn.github.com. You can do this with a command like:
host github.com 18.104.22.168
Next, open your hosts file with the following command:
sudo nano /etc/hosts
You don't have to use nano. I'm just using it for this walkthrough. Now add the following lines, with tabs in between each IP and the domain name:
22.214.171.124 github.com 126.96.36.199 avatars3.githubusercontent.com 188.8.131.52 assets-cdn.github.com
Save with Ctrl+O, and exit with Ctrl+X.
2) Flushing your DNS
This part varies based on the version of macOS you're running. I'd just follow this tutorial: https://www.igeeksblog.com/how-to-flush-dns-in-mac-os-x/
Now you should be done. Let me know if you run into any issues.