feat: Assess and improve accessibility

[lornakelly]

Description

Run an accessibility audit of the editor, document the violations and define list to fix them

Motivation

The editor ships as an embeddable npm package so it must not introduce accessibility regressions into host applications. We should verify the repo against a standard (WCAG 2.1 AA).

Proposed Implementation

• Research accessibility audit tools - vite, storybook etc
• Perform audit
• Document violations and present to team
• Fix issues based on severity

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.