CI: Add attestation to release notes

[SMoraisAnsys]

Description

Add the possibility to verify the source distribution and wheel from the release page / PyPI / workflow artifacts.
Extend the release notes in Github with information on how to verify the release's artifact attestations using GitHub CLI tool.

Issue linked

None

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have agreed with the Contributor License Agreement (CLA).

[ansys-reviewer-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.01%. Comparing base (0921006) to head (6bb294b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5906   +/-   ##
=======================================
  Coverage   85.00%   85.01%           
=======================================
  Files         161      161           
  Lines       62214    62214           
=======================================
+ Hits        52887    52891    +4     
+ Misses       9327     9323    -4     

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[MaxJPRey]

LGTM.