Fix README version badge (v2.2.1 → v2.2.3)

[omghante]

Problem

• Maven Central badge in README.md shows v2.2.1
• Actual SDK version in pom.xml is v2.2.3
• Badge is hardcoded so it doesn't update on new releases
• Confuses users checking the latest version

Proposed Changes

• Replace the static badge with a dynamic shields.io badge that fetches the latest version from Maven Central
• Badge will stay in sync with releases automatically without manual updates