Please support async generators

[keit0728]

If you try to fetch a file asynchronously and derive the cid as shown below, you will get an error saying object async_generator can't be used in 'await' expression.

import httpx
from ipfs_cid import cid_sha256_hash_chunked

async def write_chunks(url: str) -> Iterable[bytes]:
    async with httpx.AsyncClient() as client:
        async with client.stream("GET", url) as res:
            async for chunk in res.aiter_bytes():
                yield chunk

cid = cid_sha256_hash_chunked(
    await write_chunks(url="https://example.com")
)

I can avoid the above error by implementing it as shown below using cid_sha256_wrap_digest.

import httpx
from ipfs_cid import cid_sha256_wrap_digest

async def write_chunks(url: str) -> Iterable[bytes]:
    async with httpx.AsyncClient() as client:
        async with client.stream("GET", url) as res:
            async for chunk in res.aiter_bytes():
                yield chunk

async def cid_sha256_hash_async_chunked(
    data: Iterable[bytes],
) -> str:
    sha = sha256()
    async for chunk in data:
        sha.update(chunk)
    return cid_sha256_wrap_digest(sha.digest())

cid = await cid_sha256_hash_async_chunked(
    write_chunks(url="https://example.com")
)

While the above implementation works, it would be very helpful if you could implement a version of cid_sha256_hash_chunked that supports async generators (like the above cid_sha256_hash_async_chunked) in the library, so that we can use it without needing to extend it ourselves. 🙏