Add reference to joint_controller.md tutorial.

[francocipollone]

🦟 Bug fix

Fixes https://github.com/gazebosim/gz-sim/issues/2332

Summary

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

Checklist

• [x] Signed all commits for DCO
• [ ] Added tests
• [x] 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.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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