[WIP] Add 3D mesh image to README file

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Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Create a PR in nash1111/meshing based off main to add a 3D mesh image to the README, mirroring how the 2D images are generated.

Requirements:

• Follow the existing 2D example approach in examples/2d_plot.rs to create a new Rust example that generates a 3D point cloud, runs a 3D mesh (e.g., bowyer_watson_3d or another appropriate 3D meshing algorithm in this repo), and renders a static image of the resulting mesh (e.g., using plotters or another existing dependency).
• Save the generated image under examples/ (choose a clear filename like delaunay_3d_1000_points.png or similar).
• Update README.md to include the new 3D image in the Examples section next to/after the existing 2D images.
• Ensure the example is runnable via cargo run --example ... and document any new command in README if needed.
• If new dependencies are required for 3D plotting, add them appropriately and keep them minimal.

Use the existing 2D example and images as a template for style and output naming. The README currently includes:

Add the new 3D image beneath these.

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