Add a "tip" field to the store on checkout

[danirabbit]

One way to possibly increase check averages is to offer a tip field. Not sure how many people will use it, but given the option some might choose to increase their check by a couple bucks

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[lewisgoddard]

Can I get some design input on this? What should the field default to? Round up the order / nothing / a couple of dollars?

[Ayushbajpai19]

HEY, I would really like to contribute for the above issue, can you guide me through the process?