Add OpenSSF Best Practices badge to README

[liudger]

This pull request makes a minor update to the README.md file by adding a badge for OpenSSF Best Practices. This helps highlight the project's adherence to security and best practice standards.

• Documentation improvements:
  • Added the OpenSSF Best Practices badge and its associated references to the README.md to showcase compliance with best practices. [1] [2]

[Copilot]

Pull request overview

Adds an OpenSSF Best Practices badge to the project README to publicly signal adherence to recognized security and best-practice standards.

Changes:

• Added an OpenSSF Best Practices badge alongside existing project status badges.
• Added the corresponding reference-style link definitions for the badge image and target URL.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.89%. Comparing base (1115036) to head (94fa9c6).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1450   +/-   ##
=======================================
  Coverage   99.89%   99.89%           
=======================================
  Files           6        6           
  Lines         955      955           
  Branches      128      128           
=======================================
  Hits          954      954           
  Partials        1        1           

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud