Add an option to view the file content in the admin dashboard

PR #175 implemented the feature to view courses in the admin dashboard. The approve/reject admin flow for `non-BR` uploads. But currently the problem is that we cannot view the file contents/ open or download the files from the admin dashboard, rather we can just see the file name and approve or deny. Without seeing the actual file contents there is no use of seeing just the filenames to approve/reject files, as we cant know whats inside them. So, rather we should add an option to view/download the files from admin dashboard courses page too.

Stakeholders: @DreamBot706