enable async calls

[jingyi-zhao-01]

Is your feature request related to a problem? Please describe.
https://polygon.io/docs/rest/options/snapshots/option-contract-snapshot

• client.get_snapshot_option is sync,cannot leverage coroutine for multiple asynchrounus fetching.
• it's very slow when fetching each one by one.

Describe the solution you'd like

• Enable async call of this funtion version so people cacn leverage ccouroutine.

tasks = [
        client.get_contract_snapshot_async(underlying_asset, contract.ticker)
        for contract in contracts
    ]

    return await asyncio.gather(*tasks)