Add tutorial + example SDF for shadow texture size

[athenaz2]

🎉 New feature

Add tutorial + example SDF. Related to https://github.com/gazebosim/gz-rendering/pull/1034

Checklist

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