Add LoadAsync(string filename)

[pekspro]

You could load images by:

Image.Load(string path);

But there is no:

Image.LoadAsync(string path);

There are other LoadAsync methods, but they all requires a Stream. Not hard to create a FileStream, but I it would nice is this a built in from start :-)

The same is also true for the SaveAsync methods.

[JimBobSquarePants]

Sounds reasonable. Feel free to open a PR to add the functionality

[pekspro]

I created PR #1256 that adds several extensions for saving files, and PR #1257 for LoadAsync methods,