replace travis badge with docs (#546)

Co-authored-by: joel-mb <joel.moriana@gmail.com>

README.md

@@ -1,7 +1,7 @@
 # ROS/ROS2 bridge for CARLA simulator
 
 [![Actions Status](https://github.com/carla-simulator/ros-bridge/workflows/CI/badge.svg)](https://github.com/carla-simulator/ros-bridge)
-[![Build Status](https://travis-ci.com/carla-simulator/ros-bridge.svg?branch=master)](https://travis-ci.com/carla-simulator/ros-bridge)
+[![Documentation](https://readthedocs.org/projects/carla/badge/?version=latest)](http://carla.readthedocs.io)
 [![GitHub](https://img.shields.io/github/license/carla-simulator/ros-bridge)](https://github.com/carla-simulator/ros-bridge/blob/master/LICENSE)
 [![GitHub release (latest by date)](https://img.shields.io/github/v/release/carla-simulator/ros-bridge)](https://github.com/carla-simulator/ros-bridge/releases/latest)
 
@@ -20,4 +20,4 @@
 
 ## Getting started and documentation
 
-Installation instructions and further documentation of the ROS bridge and additional packages are found [__here__](https://carla.readthedocs.io/projects/ros-bridge/en/latest/).
+Installation instructions and further documentation of the ROS bridge and additional packages are found [__here__](https://carla.readthedocs.io/projects/ros-bridge/en/latest/).