Add configurable mouse button mappings to camera-controls.mjs

Summary

The camera-controls.mjs script has hardcoded mouse button mappings that cannot be overridden or customized. This makes it difficult to use the script in applications that need to reserve certain mouse buttons for other functionality (e.g., painting, selection, custom interactions).

Current Behavior

Mouse button behavior is hardcoded in the update() method (lines 730-736):

• LMB (button 0) → orbit mode
• MMB (button 1) → orbit mode
• RMB (button 2) → fly mode
• Scroll wheel → orbit mode (zoom)

There is no way to:

1. Change which button triggers orbit vs fly mode
2. Disable a specific button so an application can handle it
3. Swap button mappings (e.g., orbit with RMB, leave LMB for app use)

Use Case

I want to build an application where:

• LMB - orbit camera (handled by camera-controls)
• RMB - custom painting/interaction (handled by my app)

Similar to how the gaussian-splatting/paint.example.mjs example works, but that example uses the older orbit-camera.js script which has a separate input script that can be disabled.

Proposed Solution

Add configurable properties to control button mappings:

/**

• Mouse button for orbit mode. Set to -1 to disable.
• @type {number}
• @default 0 (LMB)
  */
  orbitButton = 0;

/**

• Mouse button for fly mode. Set to -1 to disable.
• @type {number}
• @default 2 (RMB)
  */
  flyButton = 2;

/**

• Mouse button for pan (in orbit mode). Set to -1 to disable.
• @type {number}
• @default 1 (MMB)
  */
  panButton = 1;