[dartpy] Add grid visual

[jslee02]

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Before creating a pull request

• Document new methods and classes
• Format new code files using clang-format

Before merging a pull request

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@a253a58). Click here to learn what that means.
The diff coverage is n/a.

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