Allow the user to set values of query params for studies

[johndoknjas]

Updates three functions to have optional parameters, enabling the user to set values for query params of three study endpoints. The large number of added lines is mostly due to formatting with black.

Checklist when adding a new endpoint

• Added new endpoint to the README.md
• Ensure that my endpoint name does not repeat the name of the client. Wrong: client.users.get_user(), Correct: client.users.get()
• Typed the returned JSON using TypedDicts in berserk/types/, example
• Tested GET endpoints not requiring authentification. Documentation, example
• Added the endpoint and your name to CHANGELOG.md in the To be released section (to be created if necessary)

[benediktwerner]

Thanks! You can directly set query params by passing params={"a": a} to get though. Then there's no need for the append_query_params function and manually encoding the params.

[johndoknjas]

@benediktwerner Thanks for letting me know, I've updated the PR to do this.