Add S3 instructions to documentation

You can add instructions on how to host blueprints, plugins, and themes in a S3 bucket.

Substitute:

1. __REGION__ with the region you have created the bucket, see the complete list
2. __BUCKET_NAME__ with the bucket name

In https://s3.console.aws.amazon.com/s3/buckets/__BUCKET__?region=__REGION__&bucketType=general&tab=permissions

A bucket should have this policy:

{
    "Version": "2008-10-17",
    "Statement": [
        {
            "Sid": "AddPerm",
            "Effect": "Allow",
            "Principal": {
                "AWS": "*"
            },
            "Action": "s3:GetObject",
            "Resource": "arn:aws:s3:::__BUCKET_NAME__/*"
        }
    ]
}

CORS instead must be:

[
    {
        "AllowedHeaders": [
            "*"
        ],
        "AllowedMethods": [
            "GET",
            "HEAD"
        ],
        "AllowedOrigins": [
            "*" // Here you can put https://playground.wordpress.net/
        ],
        "ExposeHeaders": [],
        "MaxAgeSeconds": 3000
    }
]

An example Blueprint that install a plugin from S3:

{
    "landingPage": "/wp-admin/plugins.php",
    "preferredVersions": {
        "php": "8.2",
        "wp": "latest"
    },
    "steps": [
        {
            "step": "login",
            "username": "admin",
            "password": "password"
        },
        {
            "step": "installPlugin",
            "pluginZipFile": {
                "resource": "url",
                "url": "https://__BUCKE_NAME__.s3.__REGION__.amazonaws.com/your-plugin.zip"
            }
        }
    ]
}

Something like: https://playground.wordpress.net/?blueprint-url=https://6251.s3.eu-west-1.amazonaws.com/fusion.json

Start by locating the documentation section covering blueprints, plugins, or themes; no specific file is named in the issue. Add the S3 bucket policy, CORS configuration, Blueprint plugin example, and hosted Blueprint URL guidance, then verify that the links and placeholders are accurate and the instructions are understandable.