Add a feature in Moodle Assignment upload -- 2

If you know php and moodle, you can do it. We want to have a feature while uploading assignment in Moodle for students. When a teacher creates an assignment in Moodle, there should be an added option to allow uploading of particular file types only. ([login to view URL] this link already has this option but is done in Moodle 1.9 version, but we use Moodle 2.3 onwards.) thats it! Please estimate the time to complete this task then bid. (no time wasters please)