Material: Sorting by View Count

User can sort materials based on their view count, because view count is one of the aspect to determine popularity.

Original Description: See popular material.

Note from TA: Popularity-based Sorting ideas were submitted by @erithiana.sisijoan, @oki.priyadi, and @reyhan.alhafizal. Thus, we decided to split the feature into 3 issues: Sorting by View Count, Sorting by Like Count, and Add "Most Popular Material" List to Homepage, each person is assigned to an issue.