add white paper endorsement page

[Moelf]

TODO:

• [x] ask people who are already in that list if they support the text on the page

[Moelf]

it might be more robust to use a google form: https://docs.google.com/forms/d/1IeLZ9s4oPG79PUjvfA2707_OlzElxgsgxj9GsbO0k1w/

(it will be filled into the sheet and auto publish iframe as well, so the presentation format is the same)

[github-actions[bot]]

Preview should be up in a couple of mins at https://www.juliahep.org/previews/PR3 (if you get a 404, wait 30s then refresh).