[CMS-578] Initial migrate to build tools docs page.

[kporras07]

Closes CMS-578

Summary

Migrating a Drupal with Composer site to a Build Tools site - Add new migrate Drupal 9 to build tools page

Remaining Work and Prerequisites

The following changes still need to be completed:

• Docs review and updates from the docs team

Release:

• When ready
• After date: $DATE

---

Post Launch

Do not remove - To be completed by the docs team upon merge:

• Redirect /docs/old-path/ => /docs/new-path/ (if applicable)
• Include/exclude pages ^ respectively within docs search service provider (if applicable)
• For Heroes - add a props post to the discussion board.
• Remove from the project board

[pantheondocs]

Lighthouse Audit Results:

Description	Live	pr-7158	Difference
Performance Score	51	63	12
Best Practice Score	79	79	0
SEO Score	96	96	0
Accessibility Score	96	96	0

Lighthouse Audit Reports:

• pr-7158 HTML Report
• Pantheon Docs HTML Report

Preview Environment

[whitneymeredith]

Preview

[whitneymeredith]

From a Docs perspective, this is good to go.