Update README.md

[eltociear]

Why are these changes needed?

Github -> GitHub

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 (a2d4b47) 33.14% compared to head (9abb1e4) 33.14%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1491   +/-   ##
=======================================
  Coverage   33.14%   33.14%           
=======================================
  Files          42       42           
  Lines        5039     5039           
  Branches     1153     1153           
=======================================
  Hits         1670     1670           
  Misses       3241     3241           
  Partials      128      128           

Flag	Coverage Δ
unittests	33.10% <ø> (ø)

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