New payment apps proposal

All,

The proposal for a spec that defines how payment apps work in the browser
has been heavily refactored. You can see the editor's draft here.

https://w3c.github.io/webpayments/proposals/paymentapps/payment-apps.html

Myself and the other editors will be working to incorporate the feedback
received to date and thoughts from the wiki Ian started over the next week.

Please provide input on the issue list with the label "Proposal: Payment
Apps":
https://github.com/w3c/webpayments/issues?q=is%3Aissue+is%3Aopen+label%3A%22Proposal%3A+Payment+Apps%22

This proposal (if it is ready) will be discussed in the meeting on 26 May
for adoption as a WG editor's draft.

Adrian