add GitHub sponsor button

Author: suren-atoyan

.github/FUNDING.yml

@@ -1,6 +1,6 @@
 # These are supported funding model platforms
 
-github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+github: [suren-atoyan]
 patreon: suren_atoyan
 open_collective: # Replace with a single Open Collective username
 ko_fi: # Replace with a single Ko-fi username