Update FUNDING.json (#5496)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>

FUNDING.json

@@ -2,6 +2,9 @@
   "drips": {
     "ethereum": {
       "ownedBy": "0xAeb37910f93486C85A1F8F994b67E8187554d664"
+    },
+    "opRetro": {
+      "projectId": "0x939241afa4c4b9e1dda6b8250baa8f04fa8b0debce738cfd324c0b18f9926d25"
     }
   }
 }