1377 Create Transactions Document

[ACStone-MTS]

What does this PR fix/introduce?

This PR introduces a document that specifically outlines the new Transaction structure and associated variants.

Closes #1377

Additional context

Document Deploy Restructure #1377

Checklist

(Delete any that aren't relevant)

• Docs are successfully building - yarn install && yarn run build.
• 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.
• My changes follow the Casper docs style guidelines.
• All technical procedures have been tested (if you want help with this, mention it in Reviewers).

Reviewers

@ipopescu

[ipopescu]

LGTM!
It would be nice to have input/output examples, but those will probably be part of the tutorials.