Add option to add ClassName with default classnames

[UsamaAshraf82]

Is your feature request related to a problem? Please describe. I am using awesome-notifications with react application The application has two theme Dark and Light In Light Theme there is no issue with awesome-notifications I have issues with awesome-notifications when Switch from light to dark mode there is no way to introduce a new className with existing one

Describe the solution you'd like I would like to use a ClassName that can be inserted with the existing classNames

so i can override the default style with my own CSS

can be easily done by

   notifier.confirm(
      `Notify`,

      () => {
      SomeCode Here
      },
      () => {
       SomeCode Here
      },
      {
        labels: {
          confirm: 'Delete Events'

        },
    **className:"DarkMode"**
      }