Aug 31 (Reuters) - Allbirds, a footwear maker backed by asset manager Franklin Templeton, said on Tuesday it has filed for a U.S. initial public offering, as the company looks to cash in on growing demand for sustainable products globally. (Reporting by Noor Zainab Hussain and Sohini Podder in Bengaluru; Editing by Ramakrishnan M.) Our Standards: The Thomson Reuters Trust Principles.