JPMorgan Chase & Co. has agreed to buy fintech startup WePay Inc. so that it can offer its technology to its 4 million small-business customers. Redwood City-based WePay helps online marketplaces and crowdfunding websites process payments. It was last valued at about $220 million when it raised funds in 2015. The companies declined to disclose the price on the deal but the Wall Street Journal cited an unnamed source who said the bank is paying about what the startup was last valued at. WePay has…