Release 3.2 mergeback

[whomwah]

This pull request prepares for the 3.2.0 release by updating the version, changelog, and release references. It introduces a comprehensive benchmarking suite, significant performance and memory improvements for SVG and HTML rendering, and updates documentation and Ruby version requirements.

Release and Documentation Updates:

• Added a new section to CHANGELOG.md for version 3.2.0, detailing major features, improvements, and changes.
• Updated changelog comparison links to reference the new 3.2.0 release.
• Bumped the gem version in lib/rqrcode/version.rb from 3.1.1 to 3.2.0.

Benchmarking and Performance Improvements:

• Added a full benchmarking suite (benchmark/), including utilities and documentation, to measure and compare performance and memory usage across export formats.
• Improved SVG rendering speed by 130% and reduced memory usage by 71%; HTML export is now the fastest and much more memory efficient.

Ruby Version and Workflow Changes:

• Raised the minimum required Ruby version to 3.2.0 and updated GitHub workflow to test only supported Ruby versions.

[andy-k]

the date...

[whomwah]

Thanks @andy-k well spotted. I'll fix 👍