Adding conversion from SphereShape to ROS msg

[Haoyangerrr-MoMo]

[Describe this pull request. Link to relevant GitHub issues, if any.] Adding convertShape for SphereShape under rviz/shape_conversion.cpp.

[Explain how this pull request was tested.]

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Before creating a pull request

• [ ] Document new methods and classes
• [x] Format code with make format

Before merging a pull request

• [x] Set version target by selecting a milestone on the right side
• [x] Summarize this change in CHANGELOG.md
• [ ] Add unit test(s) for this change

[egordon]

@Haoyangerrr-MoMo @hejia-zhang Reminder that you'll need to address these (small) changes before we can merge this PR!