docs: add funding information for github

.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+# github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+# patreon: # Replace with a single Patreon username
+open_collective: komga
+# 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
+# issuehunt: # Replace with a single IssueHunt username
+# otechie: # Replace with a single Otechie username
+# custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']