update Readme dropdown_search 5.0.2

[ricky-blip]

update Simple implementation

from this :

because is not working anymore

dropdownSearchDecoration: InputDecoration(
        labelText: "Menu mode",
        hintText: "country in menu mode",
),

to this :

dropdownDecoratorProps: const DropDownDecoratorProps(
      dropdownSearchDecoration: InputDecoration(
          labelText: "Menu mode",
          hintText: "Country menu mode",
      ),
 ),

[salim-lachdhaf]

think you for reporting that.
readme file updated in the next version which will be released today.