plugin_template

After running into the same bug 7 freaking times I have decided to use this working template implementation for ros2 pluginlib, this will be used as a reference in the future to develop plugins without riding into bugs.

• package_a: The package that contains the base implementation for the plugin
• package_b: The package contains the actual implementation for a plugin
• package_c: The package that calls the plugin from package_b

pacakge_b and package_c depend on package_a, and there is no other dependency present anywhere