Replace references to "Antonio Vivace" with "gbdev contributors"

[avivace]

There's still my name on some footers. I'd like to replace it with "gbdev contributors", maybe linking it to the "Members" (it's not complete/adherent to the actual contributions) page of the gbdev org or the "Contributors" graph of the corresponding github repository (may be more than one, e.g. this website has content contributed from other repositories).