[Feature Request] Total bytes being transferred as a formatted value + String formatting

[NickeManarin]

Hi, I noticed that the property Total of the class TransferProgress has no formatted version.
Also, it would be nice to be able to format the numbers using a string format, like {0:###,##0.0} for example.

I already implemented this on my fork both changes if you need an example:
https://github.com/NickeManarin/FileTransferManager/blob/master/IOExtensions/TransferProgress.cs#L30
And
https://github.com/NickeManarin/FileTransferManager/blob/master/IOExtensions/Helpers.cs#L29

Of course, you can ignore if these changes. Thanks.