Add endpoint to submit unlisted videos

A temporary measure which will be removed next month

https://support.google.com/youtube/answer/9230970

databases/_upgrade_sponsorTimes_15.sql

@@ -0,0 +1,10 @@
+BEGIN TRANSACTION;
+
+CREATE TABLE IF NOT EXISTS "unlistedVideos" (
+	"videoID"	TEXT NOT NULL,
+	"timeSubmitted"	INTEGER NOT NULL
+);
+
+UPDATE "config" SET value = 15 WHERE key = 'version';
+
+COMMIT;