Changed str_slug to Str::slug

`str_slug` is deprecated in Laravel 7 and above

Author: b4oshany

src/app/Models/Survey.php

@@ -2,6 +2,7 @@
 
 namespace AidynMakhataev\LaravelSurveyJs\app\Models;
 
+use Illuminate\Support\Str;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
@@ -25,7 +26,7 @@ public static function boot()
         parent::boot();
 
         static::creating(function ($survey) {
-            $survey->slug = str_slug($survey->name);
+            $survey->slug = Str::slug($survey->name);
 
             $latestSlug = static::whereRaw("slug = '$survey->slug' or slug LIKE '$survey->slug-%'")
                                 ->latest('id')