[v3] docs update: guide part

[crazywhalecc]

What does this PR do?

Add v3 docs (only guide).

Develop and Contributing part is not available yet, need more time.

Checklist before merging

If your PR involves the changes mentioned below and completed the action, please tick the corresponding option.
If a modification is not involved, please skip it directly.

• If you modified *.php or *.json, run them locally to ensure your changes are valid:
  • composer cs-fix
  • composer analyse
  • composer test
  • bin/spc dev:sort-config
• If it's an extension or dependency update, please ensure the following:
  • Add your test combination to src/globals/test-extensions.php.
  • If adding new or fixing bugs, add commit message containing extension test or test extensions to trigger full test suite.

[crazywhalecc]

Using Mermaid and Vue components, we got a cool dependency lookup page that is compatible with v3.

[netlify]

✅ Deploy Preview for venerable-pithivier-bd1a1c canceled.

Name	Link
🔨 Latest commit	13e2d0c
🔍 Latest deploy log	https://app.netlify.com/projects/venerable-pithivier-bd1a1c/deploys/69e5c96eeef7960008334874