DOC: Polish doc site

[cwang]

Is your feature request related to a problem? Please describe.

• [x] Adding GA tracking
• [x] Add social cards support
• [ ] Adding more relevant links
• [ ] Page structure
• [x] Styling in general
  • [ ] markdown styling
• [x] anchor link headings
• [ ] Build process, especially versioned API docs
• [ ] Define and target user personas/role explicitly (business champion, app admin, infra eng, project contributor etc.)

Describe the solution you'd like

Given the application nature of the project, a comprehensive user guide is expected so we should probably spend more time looking at that part of the doc site, slightly different from a typical OSS.

Describe alternatives you've considered

Happy with gh-pages and the current setup.

Additional context

N/A

[cwang]

Assigned to @janaka as you're the in-house mkdocs expert