GitHub, please, I’m begging you, add a widget to this page that lets you paste an IP and check if it’s within your IP ranges; I shouldn’t have to know CIDR notation (which the thing you link to doesn’t even support as input) to figure that out https://help.github.com/articles/about-github-s-ip-addresses/
OK I made a thing you can use https://is-this-a.github.io/ip/