Mime type option for APK installation

[bhaveshptl]

Download APK using flutter_downloader was not initiating APK installation. As mime type was setting wrong in case of APK. So Adding option to pass mime type while enqueuing download task.

[lockiechen]

Is there any progress on this PR? @hnvn

[bartekpacia]

I checked this – downloading and installing APK works. I also added an example APK file to the example app.

You mean the case where the server doesn't set the correct MIME type of a file, right?

[salmaahhmed]

APK file type works for me