Consider adding "Alternatives" section w/ comparison against `drake-ros/bazel_ros2_rules`?

[EricCousineau-TRI]

Howdy! This looks awesome, and thank y'all for posting it!

We (the Dexterous Manipulation Group in Toyota Research Institute) have been working with OpenRobotics (via contract) on the following Bazel ROS 2 rules for use within our internal codebase (Anzu) which heavily leverages Drake for manipulation.

I have filed a PR against our codebase with a preliminary attempt to categorize our different approaches:
RobotLocomotion/drake-ros#194

Two questions:

• Would y'all up for reviewing the PR to see if it's accurate / missing something?
• If it seems useful, would it makes sense to make a similar PR against this repository?

Thanks!