how to change the cart counter in a theme using theme app extension?

[anshuman9999]

I'm building a theme app extension (app embed) which has a feature of adding a specific to the cart using the cart ajax API. I'm able to add a product to the cart successfully but I can't seem to figure out how can I change the cart counter after adding the product to the cart. The cart counter actions depend on the store's theme but since I'm developing an app extension which is independent  of the theme, I'm not sure how to change the counter as well. Is there a general pattern of changing the cart counter that applies for every theme? Any help would be appreciated.

Thanks