Add tracking pixel to README

[neverett]

Why are the changes needed?

Adds tracking pixel to README per @kumare3 request.

Check all the applicable boxes

• All new and existing tests passed.
• All commits are signed-off.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.10%. Comparing base (4dd5f3c) to head (3549003).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5371   +/-   ##
=======================================
  Coverage   61.10%   61.10%           
=======================================
  Files         794      794           
  Lines       51215    51215           
=======================================
+ Hits        31296    31297    +1     
+ Misses      17038    17037    -1     
  Partials     2881     2881           

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.90% <ø> (ø)
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	68.31% <ø> (ø)
unittests-flyteidl	79.30% <ø> (ø)
unittests-flyteplugins	61.94% <ø> (ø)
unittests-flytepropeller	57.32% <ø> (ø)
unittests-flytestdlib	65.75% <ø> (+0.02%)	⬆️

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