chore: add GitHub funding configuration for Afdian

.github/FUNDING.yml

@@ -0,0 +1,4 @@
+# GitHub Sponsors and external funding links
+# https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/displaying-a-sponsor-button-in-your-repository
+
+custom: ['https://afdian.com/a/tianma-if']