Describe the feature or problem you’d like to solve

The installation instructions currently have the keys distributed from a keyserver, instead of being distributed from a key file directly(more info below).

I'm not positive on how keyservers all work, but I think that it's theoretically possible to modify the GPG key on one, and still have it download without complaint(again though, I don't really know much on how they work).

Proposed solution

Serve the GPG key directly from a URL on the GitHub CLI domain, such as https://cli.github.com/apt-key.gpg.

Other Info

If it's any kind of support for it, a lot of projects also distribute their GPG keys in the manner I described, such as:

• Docker: https://docs.docker.com/engine/install/ubuntu/#install-using-the-repository
• Atom Text Editor: https://flight-manual.atom.io/getting-started/sections/installing-atom/
• Jenkins CI: https://pkg.jenkins.io/debian-stable/

I'm open to feedback as well if I'm just not understanding how keyservers work.