try forwarding it to request section i am kind of interested but i remember there's another thread by someone that's requesting the same/similar plugin i am tempted to make one but need to re check the other thread and make sure no one want to make it/havent completed it
I spent about 30 minutes to find the thread same. I found a lot of post as my post. But it didn't have a good answer to solve it.
This should do the trick https://github.com/ThunderDoesPlugins/InventoryNotifier hopefully, i overkilled the options just for fun really
forget to note, it's not perfect, example if you fill the inventory with full stacks of 32 stone it will still says it's full