Add sample ctest cmds to tutorials

[iche033]

🎉 New feature

Summary

Added some info on how to run specific tests, similar to these instructions in gz-rendering

Test it

Checklist

• [ ] Signed all commits for DCO
• [ ] Added tests
• [ ] Added example and/or tutorial
• [ ] 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

Merging #566 (982ed84) into gz-physics6 (b83354d) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 982ed84 differs from pull request most recent head 421ed0f. Consider uploading reports for the commit 421ed0f to get more accurate results

@@             Coverage Diff              @@
##           gz-physics6     #566   +/-   ##
============================================
  Coverage        75.95%   75.95%           
============================================
  Files              143      143           
  Lines             7327     7327           
============================================
  Hits              5565     5565           
  Misses            1762     1762