documentation: ros2: run instructions for params files incorrect

[dlim04]

Describe the issue
This issue covers 3 seperate potential problems in the "Run Instructions section" of the README on the ros2 branch:

• Linked params.yml is missing.
• Steps to publish data from two devices simultaneously contains incomplete params.yml files which could be misleading.
• Running ros2 launch microstrain_inertial_driver microstrain_launch.py node_name:=sensor_a_node namespace:=sensor_a params_file:="~/sensor_a_params.yml" fails. with the following error:

user@8b30d4c51e22:~/your_workspace$ ros2 launch microstrain_inertial_driver microstrain_launch.py params_file:="~/sensor_a_params.yml"
[INFO] [launch]: All log files can be found below /home/user/.ros/log/2024-10-25-17-05-18-597342-8b30d4c51e22
[INFO] [launch]: Default logging verbosity is set to INFO
[WARNING] [launch_ros.actions.node]: Parameter file path is not a file: ~/sensor_a_params.yml
[INFO] [microstrain_inertial_driver_node-1]: process started with pid [6579]
[microstrain_inertial_driver_node-1] [INFO] [1729872318.690519498] [microstrain_inertial_driver]: Running microstrain_inertial_driver version: ros2-4.4.0
[microstrain_inertial_driver_node-1] [INFO] [1729872318.690600628] [microstrain_inertial_driver]: Using MIP SDK version: v1.0.0-283-g2c4cb6b
[microstrain_inertial_driver_node-1] [WARN] [1729872318.690605690] [microstrain_inertial_driver]: No relative position configured. We will not publish relative odometry or transforms.
[microstrain_inertial_driver_node-1] [WARN] [1729872318.690608143] [microstrain_inertial_driver]:   Please configure relative position to publish relative position data
[microstrain_inertial_driver_node-1] [INFO] [1729872318.690678571] [microstrain_inertial_driver]: Attempting to open serial port </dev/ttyACM0> at <115200>
[microstrain_inertial_driver_node-1] [ERROR] [1729872318.690696439] [microstrain_inertial_driver]: MIP SDK: Unable to open port (2): No such file or directory
[microstrain_inertial_driver_node-1] [ERROR] [1729872318.690720636] [microstrain_inertial_driver]: Failed to read configuration for node
[microstrain_inertial_driver_node-1] [ERROR] [1729872318.690723938] [microstrain_inertial_driver]: Failed to configure node base
[microstrain_inertial_driver_node-1] [FATAL] [1729872318.690727066] [microstrain_inertial_driver]: Failed to configure node
[ERROR] [microstrain_inertial_driver_node-1]: process has died [pid 6579, exit code 1, cmd '/home/user/your_workspace/install/microstrain_inertial_driver/lib/microstrain_inertial_driver/microstrain_inertial_driver_node --ros-args -r __node:=microstrain_inertial_driver -r __ns:=/ --params-file /tmp/launch_params_t30hz5c4 --params-file /tmp/launch_params_p8yuzbms'].

Modifications
Using absolute paths resolves the third problem

Additional context
These problems were encountered when trying to get started with microstrain_intertial with ROS 2.

The third problem relating to absolute paths could be a bug if relative paths for params.yml files is meant to be a supported feature.

Suggest correcting documentation in the short term and investigating a potential bug later.

[robbiefish]

Closing as the PR was merged. Thanks for the contribution