Add pub keyword to poseidon hash function

[mdvillagra]

Add pub keyword to poseidon hash function

Description

Add a pub keyworkd to the function hash of the Poseidon struct. This will allow to use the function for hashing when adding the lambdaworks-crypto package.

Type of change

Please delete options that are not relevant.

• New feature
• Bug fix
• Optimization

Checklist

• Linked to Github Issue
• Unit tests added
• This change requires new documentation.
  • Documentation has been added/updated.
• This change is an Optimization
  • Benchmarks added/run

[codecov-commenter]

Codecov Report

Merging #569 (3f1ef7e) into main (a190b17) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #569   +/-   ##
=======================================
  Coverage   95.50%   95.50%           
=======================================
  Files         112      112           
  Lines       18904    18904           
=======================================
  Hits        18054    18054           
  Misses        850      850           

Files Changed	Coverage Δ
crypto/src/hash/poseidon/mod.rs	90.47% <100.00%> (ø)

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