Add poetry dependencies to the codespaces env

[shruti222patel]

Why are these changes needed?

Ensures poetry dependencies are installed in the codespaces environment for easier setup.

Related issue number

#343

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

Merging #367 (ab7e4a9) into main (61ac640) will not change coverage.
Report is 9 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #367   +/-   ##
=======================================
  Coverage   42.33%   42.33%           
=======================================
  Files          19       19           
  Lines        2393     2393           
  Branches      539      539           
=======================================
  Hits         1013     1013           
  Misses       1302     1302           
  Partials       78       78           

Flag	Coverage Δ
unittests	42.24% <ø> (ø)

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[shruti222patel]

DO NOT MERGE -- deleting the .devcontainer/Dockerfile causes the codespace build to break even though .devcontainer/devcontainer.json points to the Dockerfile in the root directory. 🤔