Add zero! and concatenate

[mtfishman]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 79.78723% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.47%. Comparing base (62c92a0) to head (32cccc7).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/concatenate.jl	77.38%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #6      +/-   ##
==========================================
+ Coverage   69.04%   76.47%   +7.42%     
==========================================
  Files           5        9       +4     
  Lines          42      136      +94     
==========================================
+ Hits           29      104      +75     
- Misses         13       32      +19     

Flag	Coverage Δ
docs	9.09% <0.00%> (-22.49%)	⬇️

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[github-actions]

Your PR no longer requires formatting changes. Thank you for your contribution!