Add sidebar for notebooks page

[jackgerrits]

Why are these changes needed?

• Add sidebar primarily for the purpose of breadcrumbs and back navigation

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.12%. Comparing base (07520aa) to head (ac3ac3f).
⚠️ Report is 2486 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1766   +/-   ##
=======================================
  Coverage   39.12%   39.12%           
=======================================
  Files          57       57           
  Lines        6173     6173           
  Branches     1383     1383           
=======================================
  Hits         2415     2415           
  Misses       3564     3564           
  Partials      194      194           

Flag	Coverage Δ
unittests	39.12% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.