code: public function extend($provider, Closure $callback)
      {
          if ($this->isProviderAliasExists($provider)) {
              throw new InvalidArgumentException("Alias provider is already reserved [{$provider}]");
          }
  
          $this->customProviders[$provider] = $callback;
  
          return $this;
      }
docs: Register a custom file provider Closure.
  
  @param  string  $provider
  @param  \Closure  $callback
  @return \Rymanalu\LaravelSimpleUploader\Contracts\Factory
  @throws \InvalidArgumentException