Accept GeoJSON as dict not only as string

[SlowMo24]

          (Sidenote: I wonder why JSON is only supported as string and not as dict)

Originally posted by @matthiasschaub in #158 (comment)

[solo2307]

I got the same issue using ohsome-py API client when sending a request with bpolys as GeoJSON FeatureCollection:
TypeError: the JSON object must be str, bytes or bytearray, not dict

[SlowMo24]

I got the same issue using ohsome-py API client when sending a request with bpolys as GeoJSON FeatureCollection: TypeError: the JSON object must be str, bytes or bytearray, not dict

MR welcome.

Workaround would be to dump your dict as string using json.dumps(my_dict)