Allow env var to change use-path-style param of s3 config

[bestmazzo]

Description

As stated in #208 there may be scenarios where s3 storage is configured with a subdomain structure ( ://{bucket_name}.{region}.provider.com ) instead of a path structure ( ://{region}.provider.com/{bucket_name} )
hasura-storage should be able to work accordingly, but we need to extend config params

Problem

So far hasura-storage ENV vars doesn't address this kind of s3 url structure description

Solution

We should see whether passing a ENV_USE_PATH_STYLE variable to s3 config options is enough

[dbarrosop]

Hi, thanks for the contribution, a couple of minor comments.