LFDT-Lockness/cggmp21: CGGMP21_MIGRATION.md

# Migration Guide: Upgrading from `cggmp21 v0.6` to `cggmp24 v0.7` This guide provides the necessary steps to migrate your project from the older `cggmp21` protocol implementation to the latest `cggmp24` version. This upgrade is essential to align with the most recent CGGMP24 paper revision. There's