Add Liberapay to Mini-XML funding options.

.github/FUNDING.yml

@@ -4,7 +4,7 @@ github: michaelrsweet
 #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
+liberapay: michaelrsweet
 #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']