quaternion_from_euler example: input degrees

[scpeters]

🦟 Bug fix

Improve units in example program

Summary

It's easier to specify angles in degrees than radians, so change this example to accept user input in degrees.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• 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

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[codecov]

Codecov Report

Merging #282 (72d0cb2) into ign-math6 (884d67f) will not change coverage.
The diff coverage is n/a.

❗ Current head 72d0cb2 differs from pull request most recent head 83fa2da. Consider uploading reports for the commit 83fa2da to get more accurate results

@@            Coverage Diff             @@
##           ign-math6     #282   +/-   ##
==========================================
  Coverage      99.41%   99.41%           
==========================================
  Files             67       67           
  Lines           6374     6374           
==========================================
  Hits            6337     6337           
  Misses            37       37           

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[osrf-triage]

This pull request has been mentioned on Gazebo Community. There might be relevant details there:

https://community.gazebosim.org/t/new-ignition-releases-2022-03-01-citadel-edifice-fortress/1313/1