Add Unified Push to signatories

Author: marcprux

public/img/logos/unifiedpush.org.png

@@ -434,6 +434,12 @@
   social-bluesky: "https://bsky.app/profile/tuta.com"
   social-x: "https://x.com/TutaPrivacy"
   social-linkedin: "https://linkedin.com/company/tutanota"
+- organization: "Unified Push"
+  url: "unifiedpush.org"
+  poc: "Simon <mail@sgougeon.fr>"
+  region: "FR"
+  social-mastodon: "https://fosstodon.org/@unifiedpush"
+  social-x: "https://x.com/UnifiedPush"
 - organization: "VideoLAN"
   url: "videolan.org"
   poc: "Nicolas POMEPUY <npomepuy.videolabs@gmail.com>"