[ENH] - Add GitHub CLI to base image

[pavithraes]

Context

I find the github CLI quite user-friendly for common actions. E.g., checking out contributor's PRs. While it can be installed w/ conda-store, I think it's also a useful addition to the base image.

Value and/or benefit

Nicer UX for folks using GitHub, especially developer-personas.

Anything else?

Available on conda-forge: https://github.com/conda-forge/gh-feedstock

[Adam-D-Lewis]

This is straight forward to add, but everyone has custom things they want to add, potentially leading to a bloated image. It'd be nice to have a more robust way of handling this at a deployment level. We discussed a bit in the past - nebari-dev/governance#22