Improve ScaleObj

[basfroman]

• to use json.dumps see the next example

import json
from async_substrate_interface.substrate_interface import ScaleObj

id_ = ScaleObj(5)
paylod = {'jsonrpc': '2.0', 'method': 'neuronInfo_getNeuron', 'params': [23, id_], 'id': 0}

print(json.dumps(paylod, default=ScaleObj.dumper))

NOTE: json.dumps raises the error without default=ScaleObj.dumper usage.