feat: Review & improve documentation before release

[lornakelly]

Description

Review, add and update the editor's documentation ahead of the release.

Motivation

The editor's documentation is the primary interface for adopters and new contributors - for a multi-vendor project, clear docs are what make external consumption and contribution actually viable rather than aspirational

Proposed Implementation

No response

Definition of Done

• Implementation: Fully implemented according to the Serverless Workflow spec.
• Unit Tests: Comprehensive unit tests are included and passing.
• Integration Tests: Verified within the monorepo and target environments (Web/VS Code).
• Documentation: Updated README.md, ADRs, or official docs.
• Performance: No significant regression in editor responsiveness.
• Accessibility: UI changes comply with accessibility standards.