Add example for assistant invocation to readme

[ahobsonsayers]

Describe the change Add example for assistant invocation to readme

Provide OpenAI documentation link Provide a relevant API doc from https://platform.openai.com/docs/api-reference

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (4ce03a9) 98.43% compared to head (2ce2a3d) 98.43%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #639   +/-   ##
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  Coverage   98.43%   98.43%           
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  Files          24       24           
  Lines        1342     1342           
=======================================
  Hits         1321     1321           
  Misses         15       15           
  Partials        6        6           

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