Add Example to support with MinIO Configuration

[bhimrazy]

Title: Add Example to support withMinIO Configuration

Description:

The current README is great for setting up with standard AWS s3 configurations.
However, including an example for users who try to use litdata with MinIO would be beneficial.

Proposed Addition:

Add a section to the README to demonstrate how to configure litdata to work with MinIO. Below is a proposed example:
The content of the configuration file should be as follows:

[default]
aws_access_key_id = ACCESS_KEY_HERE
aws_secret_access_key = SECRET_KEY_HERE
endpoint_url = https://minio.your-domain.com # self deployed minio url

[bhimrazy]

Hi @tchaton,
Please feel free to assign me this issue.
I will be adding a PR for this issue, possibly along with a demonstrable example.