ToDo: Generate separate documentation eBook -> I've done it

[Skeeve]

Hi Steffen.

Please have a look at #24.

It now auto-generates a separate documentation eBook from the README and the puzzle's rules.

For this, perl is required but fortunately it is already present in the docker image.

I attach the auto generated file here so that you can have a look.

Pocket Puzzles.epub.zip