By Sruthi Shankar and Bansari Mayur Kamdar (Reuters) – UK stocks climbed on Thursday, with the domestically focussed FTSE 250 index hitting a one-week high, after Boris Johnson announced he would quit as British prime minister after he dramatically lost the support of his ministers. The export-oriented FTSE 100 gained 1.1%, while the FTSE 250 midcap index climbed 1.5% after Johnson’s statement. Sterling was last up 0.5% against the dollar, roughly where it was trading before Johnson resigned. The currency hit two-year lows versus the dollar on Wednesday after the resignation of top ministers l…