Improve Download UX

[pwd-github]

First off, thanks for a great app.

So I've been using the app and I have my own library and archiving system and epub reader. Issue is, when I add an epub to my library, there's no straight forward way to export it and even when I do, there's no title, just a random string. It would be good if I could just straight forwardly export to my downloads folder and it can have AUTHOR-TITLE.EXT as the filename.

[dstark5]

Sure will soon migrate from using AppLocalStorage to Device storage and also Implement the export functionality as well

Thank You