Rename JuliaHEP-2023 repo to Julia-intro

[graeme-a-stewart]

Although the tutorial was given at the workshop it clearly lives on independently. So it should be in a different repo.

Either we move it to a new repo, or we rename this one to emphasise the tutorial material (other than a few PDFs, it is the real content that's here).

[Moelf]

We can just rename the repo

[graeme-a-stewart]

I tend to agree - rename is easier. Will that affect the deployment onto juliahep.org @Moelf ?

[Moelf]

I think we just gotta update url everything and it will be fine -- the github page contains a slug for the repo name