Async support

[Niccolum]

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Issue subject

Can you create async classes, based on httpx or aiohttp client.

Expected behaviour

Async support for api

Actual behaviour

Only sync connector supported

[2pd]

It's in our list, but unfortunately, it's not in high priority.

[d3thomas]

What is the status of async support? This would be a good addition.

[Ephraim-Akolo]

I have added support for async API, and I wish to create a pull request.
The async support is based on httpx.
Replicated all tests from the sync to the async and all passed 100%.
Async requests work fine and are identical to the sync version in code
example import: from binance.async_spot import AsyncSpot
Feature branch link:here

[Jnorm911]

Bump.