update lightd main.c, add lux sensor support and test ok

guowenxue

2021-01-28 a903b916f09419e7324a2352232e601acc598d67

 apue/2.Socket/ds18b20.c

@@ -98,5 +98,7 @@
    /* convert string value to float value */
    *temp = atof(ptr)/1000;
   
    close(fd);

    return 0;
}