Introduce VitePress documentation using @cakephp/docs-skeleton

[josbeir]

Adds VitePress-based documentation for this project, powered by the new distributable CakePHP configured VitePress theme @cakephp/docs-skeleton that provides CakePHP branding, shared assets, and sensible defaults out of the box.

The skeleton follows VitePress's official distributable theme pattern, so the setup here is minimal:

• config.js extends @cakephp/docs-skeleton/config with project-specific overrides
• index.js re-exports the CakePHP theme
• All branding (fonts, favicon, icons, components, CSS) comes from the package automatically via a bundled Vite plugin
• Standard vitepress dev/build/preview commands — no custom wrappers or env vars
• Theme updates across all CakePHP docs projects are a simple npm update

Before i address the other versions i want to make sure that we have 5.x handled properly.

@LordSimal it would be great if you could introduce a dokku dockerfile to deploy this one? I removed the docs.Dockerfile from this branch but it can be introduced again using the same naming if needed.

Additionally, (also) after this is done we should swap the main doc repo's to the new node based plugin first as it is a lot easier to maintain like this.

[Copilot]

Pull request overview

This PR migrates the CakePHP Migrations plugin documentation from Sphinx/RST to VitePress/Markdown, powered by a shared @cakephp/docs-skeleton theme package. The old RST files, Python config, and Docker-based docs builder are removed in favor of a Node.js-based VitePress setup.

Changes:

• Converts all documentation from RST to Markdown format, adds a new upgrading.md guide, and removes the old Sphinx configuration
• Introduces VitePress configuration with CakePHP branding via @cakephp/docs-skeleton, including sidebar TOC, version picker, and theme setup
• Removes the old docs.Dockerfile for Sphinx-based builds

Reviewed changes

Copilot reviewed 21 out of 23 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
docs/package.json	New npm package with VitePress and docs-skeleton dependencies
docs/.vitepress/config.js	VitePress config with project-specific overrides
docs/.vitepress/theme/index.js	Re-exports CakePHP theme
docs/.vitepress/toc_en.json	Sidebar navigation structure
docs/en/*.md (new)	Markdown versions of all documentation pages
docs/en/*.rst (deleted)	Removed old RST documentation files
docs/en/conf.py, docs/config/ (deleted)	Removed Sphinx configuration
docs/en/contents.md	Table of contents in markdown
docs/en/upgrading.md	New 4.x→5.x upgrade guide
docs/.vitepress/cache/deps/*	Build cache artifacts (should not be committed)
docs/.gitignore	Git ignore for node_modules and public
docs.Dockerfile	Removed old Sphinx Docker build

Files not reviewed (1)

• docs/package-lock.json: Language not supported

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