[Documentation] Adoption guide: goals, audience, and step-by-step usage

[ashleyshaw]

What documentation is needed?

A clear adoption guide aimed at users migrating to our block themes and block-first plugins. The guide should clarify project purpose, target audience (who should or should not adopt), required technical prerequisites, and step-by-step adoption workflow (including checks, code upgrade tasks, and links to canonical org docs: https://github.com/lightspeedwp/.github/blob/develop/.github/custom-instructions.md). Address the impact on theme or plugin updates and highlight rollback/recovery steps.

Why is this documentation important?

Without a discoverable, up-to-date adoption guide, implementers risk misconfigurations, missed requirements, and technical debt. This slows onboarding, increases support queries, and undermines a consistent approach to security, accessibility, and code quality.

Acceptance Criteria

• Documentation is clear, accurate, and up-to-date
• Follows WordPress documentation standards
• Outlines project goals, audience, prerequisites
• Provides a step-by-step process
• Includes performance/a11y checks and what tools to run (e.g. PHPCS/WPCS, PHPStan, ESLint, etc.)
• Changelog entry prepared for PR if user-facing update

Additional Context

• Reference https://github.com/lightspeedwp/.github/blob/develop/.github/custom-instructions.md and any other org canons
• If possible, include a basic checklist or flow diagram for editors/migrators

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Definition of Ready (DoR)

• Documentation need is clear and well-defined
• Related docs/issues or files linked
• Acceptance criteria listed
• Estimate added if relevant
• Milestone/release assigned (if applicable)

Definition of Done (DoD)

• Documentation meets org standards and guidelines
• Changelog entry prepared for PR (CHANGELOG.md)
• Documentation reviewed for clarity and accessibility
• Screenshots/code examples included if relevant
• PR uses correct branch prefix (docs/)

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[linear-code]

LS-659