What is the name of the vendors that serve resources to schools whose primary focus area is Literature?
primary focus area is Literature refers to primary_focus_area = 'Literature'
SELECT T1.vendor_name FROM resources AS T1 INNER JOIN projects AS T2 ON T1.projectid = T2.projectid WHERE T2.primary_focus_area LIKE 'Literacy%' GROUP BY T1.vendor_name ORDER BY COUNT(T2.primary_focus_area) DESC LIMIT 1