Henderson Land Development, the city’s third-biggest private landowner, said on Friday that it was considering offering 100,000 square feet of farmland in Kam Tin, New Territories, to the government for seven years to build temporary housing to accommodate 10,000 residents.Henderson Land also said it would donate land in Yuen Long to build youth hostels and other social welfare uses. However, it was not clear how much land it intends to donate for such purposes.The move by Henderson comes after…