Fix FUNDING.yml

Author: rmm5t

.github/FUNDING.yml

@@ -6,4 +6,4 @@ github: [rmm5t]
 # 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
-custom: https://www.paypal.me/rmm5t/5
+custom: "https://www.paypal.me/rmm5t/5"