add example for extending span attributes

[rinfx]

demo for adding custom span attributes

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.74%. Comparing base (ef31e09) to head (00178f2).
Report is 365 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1936      +/-   ##
==========================================
+ Coverage   35.91%   43.74%   +7.83%     
==========================================
  Files          69       78       +9     
  Lines       11576    12479     +903     
==========================================
+ Hits         4157     5459    +1302     
+ Misses       7104     6678     -426     
- Partials      315      342      +27     

see 73 files with indirect coverage changes

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