use push_preview = true in deploydocs

[dpo]

With this change, a new workflow named "documenter/deploy" appears in the list of checks when the docs have finished building.
Clicking on "details" takes you to the docs resulting from the pull request.

[codecov]

Codecov Report

Merging #13 (c808a2f) into main (1065b71) will increase coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   71.42%   71.50%   +0.07%     
==========================================
  Files           1        1              
  Lines         196      200       +4     
==========================================
+ Hits          140      143       +3     
- Misses         56       57       +1     

Impacted Files	Coverage Δ
src/BasicLU.jl	71.50% <0.00%> (+0.07%)	⬆️

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