Added method to compute the HMAC

[deltadecay]

I've added methods and tests to compute the HMAC.

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.75%. Comparing base (10f7b7b) to head (c9a37de).
⚠️ Report is 41 commits behind head on main.

Files with missing lines	Patch %	Lines
src/OpenSSL.jl	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
+ Coverage   77.56%   77.75%   +0.18%     
==========================================
  Files           2        2              
  Lines        1083     1200     +117     
==========================================
+ Hits          840      933      +93     
- Misses        243      267      +24     

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