make docs build again

[niccokunzmann]

readthedocs is not building. It should build again. Sometimes they build and sometimes they do not. https://readthedocs.org/projects/kniteditor/builds/

Fix this for

• [ ] knittingpattern
• [ ] AYABInterface
• [ ] kniteditor

Hints:

• This may have to do with installing pillow of different versions.