Clarify versioning policy and expectations around breaking changes

[afraid-rebuke]

Overview

The base/account-sdk repository provides API usage examples and reference documentation, but it does not clearly explain how versioning is handled or what guarantees (if any) exist around backward compatibility and breaking changes.

Problem Description

Developers integrating the SDK into production systems may be unsure about:

• how often breaking changes are expected
• whether semantic versioning is strictly followed
• how to safely plan upgrades
• which releases may require code changes

This uncertainty can make long-term maintenance and upgrade planning more difficult.

Proposed Solution

• Add a short section to the README (e.g. “Versioning & Compatibility”).
• Clearly describe:
  • whether semantic versioning is used
  • how breaking changes are communicated
  • recommended practices for upgrading between major/minor versions
• Keep the guidance high-level and non-prescriptive.