Add DALLE Notebook Example

[BeibinLi]

Why are these changes needed?

More MM features. In the future, we will move the agent into contrib and the wrapper into OAI.

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 (140a023) 27.89% compared to head (61e51db) 27.89%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #744   +/-   ##
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  Coverage   27.89%   27.89%           
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  Files          27       27           
  Lines        3466     3466           
  Branches      784      784           
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  Hits          967      967           
  Misses       2428     2428           
  Partials       71       71           

Flag	Coverage Δ
unittests	27.84% <ø> (ø)

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[qingyun-wu]

LGTM. Inspiring notebook with interesting example! Thanks Beibin!

[sonichi]

Shall we add links to it in our website?
(cc @qingyun-wu)