docs: document the broadcast operator

[jponge]

Fixes #1450

[jponge]

/cc @metacosm

[codecov]

Codecov Report

Merging #1456 (5e31dc6) into main (98ccc48) will increase coverage by 0.05%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1456      +/-   ##
============================================
+ Coverage     89.31%   89.37%   +0.05%     
- Complexity     3361     3364       +3     
============================================
  Files           459      459              
  Lines         13402    13402              
  Branches       1641     1641              
============================================
+ Hits          11970    11978       +8     
+ Misses          797      795       -2     
+ Partials        635      629       -6     

see 13 files with indirect coverage changes

[metacosm]

Thank you!