Usage

@forms.ColorPicker(forms.ColorPickerProps{
    ID:    "brand_color",
    Name:  "brand_color",   // hidden input; value = hex string
    Label: "Brand Color",
    Value: "#3b82f6",        // initial hex colour
    Hint:  "HSL sliders + hex input",
})

// Listen for changes in JavaScript:
// el.addEventListener('change', e => console.log(e.detail.value))