Add donation option on cart page that will add cost in the cart.

[Anilket26]

I want to add the donation checkbox on cart page that will add the extra cost in the cart amount if checked and removed amount if checkbox unchecked.

I want to create this functionality through API because we need to create this functionality as a Shopify APP.

Kindly help me to achieve this functionality if any one worked on this. Guide with the API details and the flow how to achieve this.

Thanks