Add tutorial to access S3 by assuming role with MFA requirement.

[dkocher]

Depends on

• Add connection profile for S3 with GetSessionToken from AWS Security Token Service profiles#161
• Add connection profile for S3 with AssumeRole from AWS Security Token Service profiles#159

[Copilot]

Pull Request Overview

This PR adds a comprehensive tutorial for configuring AWS IAM users to access S3 by assuming a role with MFA requirements. The tutorial provides step-by-step instructions for setting up the necessary AWS IAM components and connecting through Cyberduck/Mountain Duck.

Key changes:

• Creates a detailed tutorial covering IAM user setup, role creation, and MFA configuration
• Adds the tutorial to the index for discoverability
• Links to the tutorial from the S3 protocol documentation

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tutorials/s3_iam_role_mfa.md	Complete tutorial with IAM configuration steps and connection instructions
tutorials/index.md	Adds the new tutorial to the table of contents
protocols/s3/index.md	References the tutorial from S3 documentation

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