Add some example input and outputs

[NightMachinery]

Most opensource image processing tools don’t quite work (and that’s fine!); Having some example images to easily gauge the tool would help potential users. Thank you.

[galfar]

There are already sample inputs in TestImages folder and outputs can be quickly generated by running runtests scripts.

What do you think would make Deskew's deskewing performance more discoverable?
Some "before" and "after" examples in Readme so it's visible directly on repo's frontpage on Github?

[GitHubRulesOK]

Interesting related https://github.com/xellows1305/Document-Image-Dewarping