Setup GitHub "Sponsor" button

.github/FUNDING.yml

@@ -0,0 +1,2 @@
+patreon: godotengine
+custom: https://www.paypal.com/donate/?token=v-mEfr__g1BbOiStnJsgwRib_I8jVSMD_064iu7NizC0Uvm9fSiPYOs-v1VQz9HFK1K8YG