Add pagination to employees endpoint

[FriedrichtenHagen]

I have received an email from personio saying that the employee endpoint will be paginated starting from 2024-12-07.
At the moment get_employees uses request_json which does not handle pagination.
Just switching to request_paginated may be enough (?).

From the personio docs:
In order to maintain system integrity and acceptable performance at V1 GET employees endpoint the maximum page size will be reduced to 100 employees per page on an ongoing basis in 2025.

The docs do not mention the deadline that I have received via email. Anyways this seems like an easy fix and I am happy to make a PR.

[FriedrichtenHagen]

I am working on a pr now.

[FriedrichtenHagen]

PR is here: #42

[klamann]

Hi, I'm not with Alexander Thamm anymore and don't have access to Personio, so I have no way to test any changes.

@at-gmbh anyone interested in maintaining this project? Otherwise it would probably make sense to fork it