Add github's IP ranges for daily import

[mrchrisadams]

Github publish their IP ranges via an API, just like how AWS, Google and Azure do.

https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/about-githubs-ip-addresses
https://docs.github.com/en/rest/reference/meta

If we had an importer like we have with AWS, any github hosted site would be able to show the commitments github has pointed to, and ideally whatever information we can point to about their transition to renewable energy.

https://github.blog/2021-04-22-environmental-sustainability-github/

This would be a good start - having the scoped breakdown of carbon emissions would be even better as they are members of the Green Software Foundation, so presumably this data exists, and the parent company is generally pretty good on reporting its direct emissions.

[mrchrisadams]

I should probably link to the other issues too:

This here was the one where we first started doing regular imports of the IPs that AWS uses:
#64

This here is the issue where we talk about how wonderful it would be if only some nice nerd at Azure would do the same for Microsoft's cloud, so we can refer users to the sustainability work going on there:
#189

And for completism, here's the one for google cloud, where there's a bit of discussion about how you could start figuring out the likely location-based carbon intensity of compute per hour based on the region:
#208

[mrchrisadams]

This is going to stay open until we have github's IP ranges imported.

I'm happy to help provide pointers on how to do this, but I won't have the time to implement this myself, ahead of other work.