feat: ColorPicker label optional

[camperking]

Hi,

thanks for this nice library! I've changed the label of the ColorPicker to an optional prop and also updated the documentation.

[lizidev]

I think adding an optional label slot would be a bit more flexible. For example:

<ColorPicker value>
        <ColorPickerLabel solt let:color>
            {format(color)}
        </ColorPickerLabel>
</ColorPicker>