Add of explanation about work

ros2_description_bolt/README.md

+# ros2_control_bolt
+----------------------
+
+Author : Paul Rouanet
+
+### What it is
+
+A description of physical properties of Bolt collected from ODRI (robot_properties).
+
+The meshes of each actuators and of the body are in "meshes".
+
+### In ros2_control :
+
+system_bolt.ros2_control.xacro :
+
+Definition of all data usefull for system_bolt.cpp (ros2_hardware_interface_bolt) :
+
+   - Ethernet connexion name
+   - Each joint with :
+      - Name
+      - Min and max values about position, velcity, effort, gain_kp and gain_kd
+      - State values for the same data
+      - Properties of each joint : offset, number, polarity ...
+   - The IMU with :
+      - x, y, z values of gyroscope, accelerometer, linear_acceleration, attitude_euler
+      - x, y, z, and w values of quaternion
+      
+### In urdf
+
+leg.xacro : all URDF data about legs
+
+system_bolt.urdf.xacro : global doc that calls leg.xacro
+
+system_bolt_description.urdf.xacro : this doc calls ALL the others