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 ✅

Comparison is base (a34e4cc) 39.35% compared to head (1079c5c) 39.02%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1766      +/-   ##
==========================================
- Coverage   39.35%   39.02%   -0.34%     
==========================================
  Files          57       57              
  Lines        6093     6173      +80     
  Branches     1362     1383      +21     
==========================================
+ Hits         2398     2409      +11     
- Misses       3499     3570      +71     
+ Partials      196      194       -2     

Flag	Coverage Δ
unittests	39.02% <ø> (-0.34%)	⬇️

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