submission form: info to github repo is confusing

[pbellec]

we should ask for the link to the github repo, rather than ask for the user/organization and then repo name. This confused me and roboneurolibre ended up trying to clone simexp/https://github.com/SIMEXP/vcog_hps_ad

Also, google form is great and easy to set up, but ideally we would be able to check that the url resolves while filling the form, because now I need to redo the entire submission to fix that step.