I'd like to show an alert if I select a file .zip or .rar by mime type (not extension).

But i don't know what's the exact, if exist, method of this plugin.

```
$("#file").fileinput({
                    'language': 'it',
                    maxFileCount: 1,
                    'showPreview':true,
                    'removeFromPreviewOnError': true,
                    'showUpload':false,
                    maxFileSize: 25600,
                    allowedFileExtensions: ["jpg", "gif", "png", "zip", "rar", "pdf", "doc", "docx", "xls", "xlsx"]
                }).on('fileselect', function(event, numFiles, label) {

                    // check mime type for zip or rar ?? how ??

                    if ( mime == "zip" || mime == "rar" ) {

                    alert(label + " is an archive file");

                    }
                });

```