Amid a slide that’s seen its shares shed 40 per cent of their value since November, Shopify is partnering with a Chinese e-commerce powerhouse in a bid to make it easier for its U.S.-based merchants to sell their goods in the world’s most populous market. The Ottawa-based software giant announced this week it’s struck a deal with JD.com that will allow merchants in the United States that run online stores using Shopify’s software to list their wares on JD’s global e-commerce platform, known as JD Worldwide. Shopify said the new sales channel, which launched on Tuesday, opens the door to…