Update documentation about classification V2

[fmigneault]

@fmigneault cloned issue crim-ca/mlm-extension#24 on 2024-05-22:

🚀 Feature Request

Given that stac-extensions/classification#48 is merged (see stac-extensions/classification#51), the corresponding https://github.com/stac-extensions/classification/releases/tag/v2.0.0 should be referenced in examples and the best practices in order to ensure counter-validation by the extension of mlm:output including a nested classification:classes property.

🔉 Motivation

Use latest references and definitions that integrate well together.

Also, this allows to officially add the https://stac-extensions.github.io/classification/v2.0.0/schema.json reference to stac_extensions since the field would be found and validated.

📡 Alternatives

📎 Additional context