docs: add section on aws codeartifact

[rayduck]

In the documentation, there isn't a tab for authenticating to AWS codeartifact, but I stumbled upon the relevant issue #1783 and the linked blog post.

I managed to set up keyring authentication using the newer pixi global install method (as opposed to the pipx workaround in the older blog post). In my case, I have left keyringrc.cfg empty (there are good defaults as mentioned in the docs) so it wasn't a necessary step.

I hope this will help others who are using codeartifact too.

[ruben-arts]

Thank you!