* Add initial architecture document

* Apply suggestions from code review

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* Move text to `codegen` crate docs

* Update text

* Add 'v1' and 'v2' to spellcheck dic

* Add text about execution environment

* Apply suggestions from code review

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* Minor clarification

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>