Fix typo in README.md

[eltociear]

Why are these changes needed?

functionalites -> functionalities

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.

[gagb]

PR fixes a spell error in readme.

[codecov-commenter]

Codecov Report

Merging #37 (eb6bc84) into main (d3d5dca) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #37   +/-   ##
=======================================
  Coverage   35.16%   35.16%           
=======================================
  Files          17       17           
  Lines        1965     1965           
  Branches      432      432           
=======================================
  Hits          691      691           
  Misses       1223     1223           
  Partials       51       51           

Flag	Coverage Δ
unittests	35.11% <ø> (ø)

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