Add template folder people can download for their own projects

[RichardPfr]

If we provide a more detailed installation and setup guide as described in pyroll-project/pyroll-docs#15 we may also provide a basic set of files people can use and download to setup their own projects.

This may or may not include:

• prepared hatch.toml files
• prepared pyproject.toml files
• prepared jupyter notebooks with basic skeletons

[ChRen95]

I would also bring a bit more structure using folders.
Also this would bring a bit more advertisement to the Kalibreurstag if we but all notebooks that were created there into the respective folder. And further have a folder for general examples.