Updated the Zip file with the following folder structure:

• itemsadder-new containing the new ItemsAdder add-on structure (versions 3.3.0 onwards).
  
• itemsadder-old containing the old ItemsAdder add-on structure (versions 3.2.5 and older).

I made a blog post covering how you can migrate your old add-ons:
https://www.andre601.ch/blog/posts/2022/11-21-itemsadder-3.3.0/