GeezerVison

Resolves #5

Fills in the Processing 5.0 (Java) page under getting-started, based on processing4's BUILD.md and processing/processing4#1582.

Changes:

• Requirements: JDK 25, Rust, jextract and Git, with a Windows note about the Microsoft C++ Build Tools
• Build: clone with --recursive, then build with -PenableWebGPU=true
• Run: start the PDE with the WebGPU flag and try a short test sketch
• Troubleshooting: Gradle download timeout, "link.exe not found", Permission denied, missing libprocessing submodule

The page status is draft.

Checked:

• npm run build passes
• On Windows 11, Gradle 9.1.0 installed and the Rust build started with -PenableWebGPU=true. The Gradle timeout and "link.exe not found" errors are ones I hit myself.

Not checked:

• I did not get a full build, so the "Run the WebGPU examples" steps are untested. I marked that section with a todo. Confirmation from someone with a working build would be welcome.