1378 Type Documentation and Serialization Standard Update

[ACStone-MTS]

What does this PR fix/introduce?

This PR updates the serialization standard with new types for Casper 2.0.

Closes #1378

Additional context

Document Type Extensibility #1378

Checklist

(Delete any that aren't relevant)

• [x] Docs are successfully building - yarn install && yarn run build.
• [x] For new internal links I used relative file paths (with .md extension) - e.g. ../../faq/faq-general.md - instead of introducing absolute file path, or relative/absolute URL.
• [x] My changes follow the Casper docs style guidelines.
• [x] All technical procedures have been tested (if you want help with this, mention it in Reviewers).

Reviewers