Add navigating to other files within the same folder.

[stymbhrdwj]

Is your feature request related to a problem? Please describe.
When I have multiple images in one folder I need to compare back and forth with, I have to open separate instances of the viewer in different windows, which is tedious when there are multiple files.

Describe the solution you'd like
It would be helpful to have an option to go to the next file or the previous file in the folder using the arrow keys, similar to how eog does it in Gnome's Image Viewer.

Describe alternatives you've considered
I have tried opening all files in tabs but I cannot open multiple files at once. I have to open them one by one.

Additional context
I am using version 0.6.1 in Arch Linux.