send fellowship invitation to both profile and contributor emails

scipost_django/templates/email/fellowship_nominees/fellowship_invitation_initial.json

 {
     "subject": "Invitation to become a Fellow at SciPost",
     "recipient_list": [
-        "nomination.profile.email"
+        "nomination.profile.email",
+        "nomination.profile.contributor.user.email"
     ],
     "bcc": [
         "edadmin@"