Add reference to joint_controller.md tutorial.

[francocipollone]

🦟 Bug fix

Fixes #2332

Summary

Adds a reference in tutorials.md.in file to joint_controllers.md tutorial.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[azeey]

Thank you!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.95%. Comparing base (7143110) to head (c24c1f1).

Additional details and impacted files

@@           Coverage Diff            @@
##           gz-sim8    #2333   +/-   ##
========================================
  Coverage    65.95%   65.95%           
========================================
  Files          327      327           
  Lines        31348    31348           
========================================
  Hits         20676    20676           
  Misses       10672    10672           

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