[Python-ideas] Propouse add context to json module.

JSON serialization used in many different libraries without the ability for configuration (Example https://github.com/aio-libs/aioredis/blob/8a207609b7f8a33e74c7c8130d97186e78...). Propose to add something like the context in the decimal module, wIch will contain all global configs for dump and load functions.

Thanks!