HONG KONG, June 24 : The U.S. dollar extended gains to reach a fresh 13-month high against a basket of major currencies on Wednesday, as investors sought shelter from a tech stock selloff and prepared for rate hikes from the Federal Reserve.  Stock market volatility continued after a broad selloff of technology and semiconductor sectors dragged global shares lower, sparking safe-haven demand for the dollar and bonds. Meanwhile, expectations of a U.S. rate hike continued to build with Fed