Update funding to include Ko-fi link

.github/FUNDING.yml

@@ -1,10 +1,10 @@
 # Currently used
 patreon: EssentialsX
+ko_fi: essentialsx
 
 # Currently not used
 #github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
 #open_collective: # 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
 #liberapay: # Replace with a single Liberapay username