Update Makefile & scripts from upstream

[tkphd]

No description provided.

[bkmgit]

When contributing, an assumption is made that the repository will be cloned onto the desktop. For lessons, many edits may be done in the browser without cloning to the desktop, so the wording can possibly be generalized and a link added to https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-and-deleting-branches-within-your-repository

Asking people to work on a branch and then make pull requests from the branch is helpful. See for example https://githubflow.github.io/

[tkphd]

Completely agreed, @bkmgit. We should work these links into our Contributing guides, thanks!
Was this comment meant for #37?

[bkmgit]

It does apply to #37 but description may also be useful in explaining how people can contribute.