Add rumbleController API and Blockly block for gamepad haptics

[tracygardner]

Motivation

• Provide a simple cross-platform API to trigger controller vibration/haptics from scripts and Blockly, enabling richer tactile feedback in experiences.

Description

• Add rumbleController(controller = "ANY", strength = 1, durationMs = 200) implementation in api/xr.js that normalizes inputs, locates a matching gamepad, and uses vibrationActuator or hapticActuators to play effects or pulse, returning Promise<boolean>.
• Expose rumbleController in the public flock API and include it in the side-effect API list in flock.js.
• Add a Blockly block definition in blocks/xr.js, a JS code generator in generators/generators.js, a toolbox entry in toolbox.js, and English localization/tooltip in locale/en.js.
• Document the new function in API.md with parameters, return value, and an example.

Testing

• Ran the project build (npm run build) and the test suite (npm test) after changes, and both completed successfully.
• Linting (npm run lint) was executed and showed no new errors related to these changes.

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Codex Task