A six-year-old British girl from south London in the UK found a Christmas card with a message allegedly from foreign prisoners in China. The sender of the message claimed that prisoners were being forced to work against their will in the Shanghai Qingpu prison. The holiday card, which is among those sold to raise money for charity, was bought from British supermarket chain Tesco. The retailer said it has halted production at a Chinese factory after the discovery and launched an investigation…