Run hector-mapping with turtlebot3 in gazebo

1. env

   ROS Melodic

   ros-melodic-turtlebot3* installed

2. run gazebo

    roslaunch turtlebot3_gazebo turtlebot3_world.launch
   

3. run hector

    roslaunch turtlebot3_slam turtlebot3_slam.launch slam_methods:=hector
   

4. control with teleop

    roslaunch turtlebot3_teleop turtlebot3_teleop_key.launch
   

   Now, use keyboard control the robot.