Override empty results title

[nemanja-nisic]

First of all, great library, works awesome and easy to use.

When there are no results I get 'No matching items.' message, I would like to be able to override this. In my case I have different languages so this is necessary.

Other than that, maybe add an option to provide our own loader or at least change colour.

[abangadit]

you can create TextFieldSearch.dart on your project and copy the source, then you can customize the text all you want