fix: don't override `per_page` in `PaginatedList`

[superle3]

Proposed Changes

• Don't override per_page parameter
• update readme to state 100 is used instead of the 10 default when it is not specified, but we specify it already by default
• add _kwargs as arg to PaginatedList and change every kwargs=combine_kwargs(**kwargs) to _kwargs=combine_kwargs(**kwargs), since I couldn't find a reason why some were different in the documentation and commits.
• specify the per_page parameter in the mock requests.

Fixes #685 .

TODO: a test maybe?

[superle3]

fixtures were wrong, updated them and the tests accordingly.