Add support for draft PRs

[mattprecious]

This is just a parameter that can be passed into createPullRequest(), but draft PRs are not supported on all GitHub repositories. From https://docs.github.com/en/rest/pulls/pulls?apiVersion=2022-11-28#create-a-pull-request:

Draft pull requests are available in public repositories with GitHub Free and GitHub Free for organizations, GitHub Pro, and legacy per-repository billing plans, and in public and private repositories with GitHub Team and GitHub Enterprise Cloud.

There's an API to check if the repository is public, but nothing I can find to check if the repository owner is GitHub Team or GitHub Enterprise Cloud.