Add file types to media library filters

functions.php

/************** ADD FILE TYPES TO MEDIA LIBRARY FILTERS ****************/
add_filter( 'post_mime_types', 'custom_mime_types' );
function custom_mime_types( $post_mime_types ) {
        $post_mime_types['application/msword'] = array( __( 'Word Docs' ), __( 'Manage Word Docs' ), _n_noop( 'Word Docs <span class="count">(%s)</span>', 'Word Docs <span class="count">(%s)</span>' ) );
        $post_mime_types['application/vnd.ms-excel'] = array( __( 'Excel Files' ), __( 'Manage Excel Files' ), _n_noop( 'Excel Files <span class="count">(%s)</span>', 'Excel Files <span class="count">(%s)</span>' ) );
        $post_mime_types['application/vnd.ms-powerpoint'] = array( __( 'PowerPoint Files' ), __( 'Manage PowerPoint Files' ), _n_noop( 'PowerPoint Files <span class="count">(%s)</span>', 'PowerPoint Files <span class="count">(%s)</span>' ) );
        $post_mime_types['application/pdf'] = array( __( 'PDFs' ), __( 'Manage PDFs' ), _n_noop( 'PDFs <span class="count">(%s)</span>', 'PDFs <span class="count">(%s)</span>' ) );
        $post_mime_types['application/zip'] = array( __( 'ZIPs' ), __( 'Manage ZIPs' ), _n_noop( 'ZIP <span class="count">(%s)</span>', 'ZIPs <span class="count">(%s)</span>' ) );
        
        return $post_mime_types;
}