Tip Jar

I've had a lot of requests to add a tip feature here :) Absolutely no expectation to receive any! But just to have the option there available
Thank you <3

I've made the "options" with the purpose of them being stackable in your cart to customise the amount you'd like to tip - e.g to give a 30 pence tip = 3 x 10p - I hope that makes sense!