EML scanner enchancement

[babenek]

Description

Please include a summary of the change and which is fixed.

• Add deep attachement scan in EML
• fix mypy issues
• Documentation update
• Benchmark scores update

How has this been tested?

Please describe the tests that you ran to verify your changes.

• UnitTest
• Benchmark

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 90.52%. Comparing base (2efea3f) to head (cf91934).
Report is 2 commits behind head on main.

Files	Patch %	Lines
credsweeper/deep_scanner/eml_scanner.py	83.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #525      +/-   ##
==========================================
- Coverage   90.53%   90.52%   -0.01%     
==========================================
  Files         127      127              
  Lines        4394     4400       +6     
  Branches      707      708       +1     
==========================================
+ Hits         3978     3983       +5     
- Misses        274      275       +1     
  Partials      142      142              

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[kmnls]

Agree