chore: add github funding file

Author: Charlike Mike Reagent

.github/FUNDING.yml

@@ -0,0 +1,13 @@
+ko_fi: tunnckoCore
+
+# Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']
+custom:
+  - https://gumroad.com/l/tunnckoCoreRecurringDonation
+
+# github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+#open_collective: # Replace with a single Open Collective 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
+#issuehunt: # Replace with a single IssueHunt username
+#otechie: # Replace with a single Otechie username