Add first version of docs

[mstoelzle]

@solangegbv I started adding some Docs for the package. The instructions for building and serving the docs on the localhost were added to the README.

For now, let's put the emphasis on the API documentation. We can polish the Examples and the Quick Start guide later...

[solangegbv]

@mstoelzle
Is there a more suitable way of documenting my class to obtain something readable?

[mstoelzle]

@solangegbv I guess this part is not necessary, as at least the methods are documented separately below in the docstring of each method. I am using MKDocs. You could have a look at other examples of APIs that use MKDocs, for example, FastAPI.

Here, you can see the structure used to document the APIRouter class: https://github.com/fastapi/fastapi/blob/master/fastapi/routing.py#L596 with the resulting Doc. page: https://fastapi.tiangolo.com/reference/apirouter/