.txt extension added on downloaded files on iphone

Hi,

I have a problem that happen only on Iphone, the .txt extension is added at the end of the file when downloaded.
It seem to work fine on other devices (even on safari on mac)

Simple sample code that I use:
```
var blob = new Blob([content], {type: "text/plain;charset=utf-8"});
FileSaver.saveAs(blob, this.workout.name+'.zwo');
```

For example on Iphone, this will give the file a "workout.zwo.txt" name instead of a "workout.zwo"

Is there a way to fix this ?

Thanks