added few more artist on the dummy data file

sql/dummy_data.sql

 
 INSERT INTO artist (id, first_name, last_name)
-        VALUES (NULL, 'Burning', 'Spear'), (NULL, 'Lucky', 'Dube');
+        VALUES (NULL, 'Burning', 'Spear'), (NULL, 'Lucky', 'Dube'),
+(NULL, 'William', 'Lucky'),(NULL, 'Britney', ' Spears')
+
+
+;