Support .= syntax

[charleskawczynski]

Closes #17.

I'm a little weary of these changes, as I think it could open the door to subtle bugs.

[codecov]

Codecov Report

Attention: Patch coverage is 77.27273% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 69.15%. Comparing base (0d6c83c) to head (41fa27b).

Files	Patch %	Lines
src/collection/utils.jl	50.00%	3 Missing ⚠️
src/collection/fused_assemble.jl	87.50%	1 Missing ⚠️
src/collection/fused_direct.jl	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #26      +/-   ##
==========================================
+ Coverage   68.85%   69.15%   +0.30%     
==========================================
  Files           8        8              
  Lines         183      201      +18     
==========================================
+ Hits          126      139      +13     
- Misses         57       62       +5     

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