Dallas philanthropist Lyda Hill has devoted much of her giving to tackling social problems through science. Over the last few years, the grantmaker also has ventured into media production: financing and helping develop a TV series, “Mission Unstoppable,” aimed at girls aged 13 to 17, which features women succeeding in science, technology, engineering, and math, or STEM, careers. The CBS series — which is one part entertainment and one part feminist career inspiration — has averaged a million broadcast viewers in its first two seasons and has been nominated for multiple Emmy awards.