DOC: Show how to authenticate with fsspec's storage_options dict

[Kezzsim]

Describe the issue linked to the documentation

In the Zarr storage guide there is an example showing how to connect to an S3 bucket anonymously and read data. This is great! Yet I think a lot of people experimenting with this feature on their local machines using minio will have problems authenticating and testing using this example. I've combed through massive amounts of fsspec documentation yet I can't find what keys are acceptable for this in storage_options.

I've tried:

import zarr
import numpy as np

store = zarr.storage.FsspecStore.from_url(
    'http://localhost:9000',
    storage_options={
        'key': 'minioadmin',
        'secret': 'minioadmin'
        }
)
zarr.open_group(store=store, mode='w')

along with:

storage_options={
    'username': 'minioadmin',
    'password': 'minioadmin'
}

I know I can get a solution working with s3fs:

import zarr
import s3fs
import numpy as np

bucket = "buck"
name = "sample"

s3 = s3fs.S3FileSystem(
    client_kwargs={"endpoint_url": "http://localhost:9000"},
    key="minioadmin",
    secret="minioadmin",
    use_ssl=False,
)
s3store = s3fs.S3Map(root=f'{bucket}/{name}', s3=s3)

However, this is nowhere near as sleek and integrated as the Zarr docs make it seem.

Suggested fix for documentation

We're looking to avoid errors like:
TypeError: ClientSession._request() got an unexpected keyword argument 'secret'
Suggest a way we can add documentation to let users know what keys are valid in storage_options or where auth should otherwise be specified.