feat: Implement Sponsors.

data/migration/v13-v14/migration.sql

@@ -0,0 +1,7 @@
+BEGIN;
+
+ALTER TABLE bot_config ADD COLUMN sponsor_prompt TEXT;
+ALTER TABLE bot_config ADD COLUMN sponsor_message TEXT;
+
+INSERT INTO VersionHistory (version, author) VALUES (14, 'v13-v14 migration');
+COMMIT;