Fix stale ColorPickerController API examples in README and docs site

[iprashantpanwar]

• README.md: replace removed setWheelRadius/setWheelColor/setWheelAlpha/setWheelImageBitmap calls with direct property assignment (wheelRadius, wheelColor, wheelAlpha, wheelBitmap)
• README.md: replace removed setPaletteContentScale controller method with the paletteContentScale parameter on ImageColorPicker
• docs/ApiControllerScreen.kt: same wheel property fix
• docs/ApiImageColorPickerScreen.kt: same paletteContentScale fix

🎯 Goal

ColorPickerController's public API was refactored at some point, the wheel
customization functions (setWheelRadius, setWheelColor, setWheelAlpha,
setWheelImageBitmap) became plain properties, and setPaletteContentScale
was replaced by a paletteContentScale parameter on ImageColorPicker. The
README and the documentation website were never updated to match, so
copy-pasting these examples currently fails to compile. This PR brings both
docs surfaces back in sync with the current API.

🛠 Implementation details

• README.md "Custom Wheel" section: replaced the four .setWheelXxx(...)
  calls with direct property assignment on the controller
  (controller.wheelRadius = ..., etc.)
• README.md "PaletteContentScale" section: replaced
  controller.setPaletteContentScale(...) with the paletteContentScale
  parameter on the ImageColorPicker composable
• docs/src/wasmJsMain/kotlin/docs/screen/ApiControllerScreen.kt: applied
  the same wheel property fix to the live docs site's code sample
• docs/src/wasmJsMain/kotlin/docs/screen/ApiImageColorPickerScreen.kt:
  applied the same paletteContentScale fix to the live docs site's code
  sample

No functional/library code was changed this PR only touches documentation
(README.md) and the docs website's Kotlin/Wasm source (docs/ module).

✍️ Explain examples

Before ((unresolved reference - these methods don't exist on ColorPickerController):

controller.setWheelRadius(40.dp)
controller.setWheelColor(Color.Blue)
controller.setWheelAlpha(0.5f)
controller.setWheelImageBitmap(imageBitmap)

After:

controller.wheelRadius = 40.dp
controller.wheelColor = Color.Blue
controller.wheelAlpha = 0.5f
controller.wheelBitmap = imageBitmap