Feat: OnThisPage Component for SchemaDocumentation page

Summary

This merge request introduces:

A reusable On This Page component to dynamically generate a Table of Contents (TOC) from headings in the HTML content. Integration of this component into the content on Schema Documentation Page.

Key Features

On This Page Component:

Dynamically parses HTML content to generate a structured TOC. Supports hierarchical headings (h1 through h6), rendered in a nested format. Provides smooth scrolling to the selected section upon clicking a TOC item. Lazy loads content to ensure proper processing after HTML is parsed.

Schema Documentation Page Integration:

Introduces the Schema Documentation layout. Renders the MDX-based Schema content as static HTML using ReactDOMServer.renderToString. Passes the rendered HTML to the OnThisPage component for TOC generation. Includes a ScrollToTop button for enhanced user navigation.

Task: #54451