Not easily, nginx comes from the alpine package repo. We are currently on the latest stable, 3.8, which uses libressl, which doesn't yet support TLS 1.3. However, the edge build of nginx is using openssl 1.1.1, which supports TLS 1.3. When 3.9 stable of alpine is released, it should support TLS 1.3 with nginx.
Or you _could_ try and install nginx from the edge repo inside the container but we don't support it, so don't come to us if you try and have issues.