Heterogeneous Narwhal English Spec

[isheff]

Task description

We need to formalize our version of Heterogeneous Narwhal in english, in such a way that at least other Anoma developers can tell what is supposed to happen.

A version exists on specs.anoma.net, but it's extremely technical and may not reflect the most recent design choices.

Sub-tasks

• [ ] https://github.com/anoma/specs/issues/306
• [ ] update specs.anoma.net with similar content to the TeX version.

Definition of Done

• We have a human-readable document of the mempool layer architecture on specs.anoma.net