chore(ci): add Ruby 3.1 to CI build

[bednar]

Proposed Changes

Add Ruby 3.1 to CI build.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• rake test completes successfully
• Commit messages are conventional
• Sign CLA (if not already signed)

[codecov-commenter]

Codecov Report

Merging #109 (81af86a) into master (81af86a) will not change coverage.
The diff coverage is n/a.

❗ Current head 81af86a differs from pull request most recent head 2b2f386. Consider uploading reports for the commit 2b2f386 to get more accurate results

@@           Coverage Diff           @@
##           master     #109   +/-   ##
=======================================
  Coverage   51.07%   51.07%           
=======================================
  Files          65       65           
  Lines        6349     6349           
=======================================
  Hits         3243     3243           
  Misses       3106     3106           

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