document / write an example of approving a website

[tyrcho]

I think we could use approvals-java together with something like selenium to extend the concept of approval testing to UI testing.

This might be an Epic rather than a Story ... Possible steps:

• check that approving an image works (probably need to integrate new reporters which support image diff like this one). We'll also need to define what kind of files a reporter supports (Image / Text / ???).
• check it also works on CI (with no software installed, how to do image diff in pure java ?)
• document approving an image
• document how to get an image from a website (using Selenium for instance - SO)
• optionnally document how to get an image from a Swing application (using Java Robot)
• give a full example explaining the approach

Inspiration:

• https://www.infoq.com/news/2018/05/automated-visual-testing
• https://github.com/AppraiseQA/appraise/blob/master/README.md/