chore: add a funding JSON file to apply for Optimism rPGF round 5 (#2940)

Author: p-shahi

funding.json

@@ -0,0 +1,5 @@
+{
+    "opRetro": {
+      "projectId": "0xc71faa1bcb4ceb785816c3f22823377e9e5e7c48649badd9f0a0ce491f20d4b3"
+    }
+  }