Update HF Workflow documentation

[egrace479]

Clarify the PR first method and distinguish more from the GitHub Workflow.

[egrace479]

@thompsonmj, I think you have documentation you were going to add to this?

[egrace479]

I think we should at least link to, if not highlight, the nuances of each mode of interaction for PRs on HF in this page. In particular, I want to make sure that we keep this note for interacting through the UI, as it is one of the most common questions I get. Additionally, we could update the image to include a circle at the place to click (another suggestion I've received).

It is probably also worthwhile to keep the git PR instructions with the way we highlight the difference from GitHub. However, this could be moved to the end (paralleling the new organization coming on the Dataset Upload Guide, where git lfs is the last method).

[hlapp]

I agree a red circle or oval or some other highlight method would be helpful. I took me a (only short!) moment to match text to screenshot, but I also already know pretty well what I'm looking for, so am arguably not a good example.