feat: split out docs/guidelines routes from shared MdxRoute file

[jderochervlk]

This pull request adds support for a new "docs/guidelines" section to the documentation site. It introduces a dedicated route and loader for guideline pages, ensures proper routing and filtering, and updates the layout to match other documentation sections.

Routing and page loading:

• Added a new route handler DocsGuidelinesRoute with a corresponding loader to render markdown files from markdown-pages/docs/guidelines, extract metadata, build a table of contents, and set up the page layout. (app/routes/DocsGuidelinesRoute.res, app/routes/DocsGuidelinesRoute.resi) [1] [2]
• Updated the main routes configuration to scan and include all guideline markdown files as routes, similar to how manual and react docs are handled. (app/routes.res) [1] [2]

Routing logic and filtering:

• Modified the MDX routes filter to exclude "docs/guidelines" paths from generic MDX handling, ensuring they are handled by the new dedicated route. (app/routes.res)
• Updated the fallback logic in MdxRoute to properly handle "docs/guidelines" paths, so they render with the correct layout when matched. (app/routes/MdxRoute.res)

[github-actions]

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