A Chinese company is the latest electric-car start-up to mount a challenge to the world's best-selling electric car, the Tesla Model Y. Xpeng – which sells vehicles in China and Europe – has introduced the G6, a five-door mid-sized electric SUV, in its home market. The Xpeng G6 is priced from RMB209,900 ($AU45,000), undercutting the Tesla Model Y which starts from RMB263,900 ($AU56,500). Australian plans…