More general block types in broadcast style

[mtfishman]

Split off generalizing block sparse broadcast style from #136.

[codecov]

Codecov Report

Attention: Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.

Project coverage is 75.20%. Comparing base (f991254) to head (a238b61).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/blocksparsearrayinterface/broadcast.jl	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
- Coverage   75.29%   75.20%   -0.09%     
==========================================
  Files          35       35              
  Lines        1809     1823      +14     
==========================================
+ Hits         1362     1371       +9     
- Misses        447      452       +5     

Flag	Coverage Δ
docs	7.58% <42.10%> (-0.18%)	⬇️

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