Ваша функция должна быть такой:
public function add(Request $request)
{
request()->validate([
'image' => 'required|image|mimes:jpeg,png,jpg,gif,svg|max:2048',
]);
$imageName = time().'.'.request()->image->getClientOriginalExtension();
request()->image->move(public_path('images'), $imageName);
return back()->with('success','You have successfully upload image.');
}