Add open collective link

Author: sansyrox

.github/FUNDING.yml

@@ -2,7 +2,7 @@
 
 github: [sansyrox] # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
 #patreon: # Replace with a single Patreon username
-#open_collective: # Replace with a single Open Collective username
+open_collective: robyn_oss # Replace with a single Open Collective username
 #ko_fi: # Replace with a single Ko-fi username
 #tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
 #community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry