Feature request: add tree field to Commit

[schlichtanders]

trafficstars

Hi there,

I am currently trying to get the git tree from a specific repository's default branch, but it fails because Commit does not have the tree property

The tree property is officially documented, hence it would be great if GitHub.jl could support it https://docs.github.com/en/rest/git/commits?apiVersion=2022-11-28#get-a-commit