Write setup instructions in README.md

[adityapande-1995]

The first page readme does point to ros2_examples_bazel_installed and other directories for detailed instructions, but it might not be clear to users who may want to build and test all of them, or just know the setup instructions for drake and any other prerequisites. A snippet like this can be included in the landing page README :

# Steps to build drake_ros using bazel on ubuntu:jammy

mkdir drake_stuff
cd drake_stuff

git clone [email protected]:RobotLocomotion/drake.git
git clone [email protected]:RobotLocomotion/drake-ros.git

# Install dependencies
sudo apt install -y python3 python3-toposort python3-rosdep

yes | sudo ./drake/setup/ubuntu/install_prereqs.sh

# Add ros repos
sudo apt update && sudo apt install curl -y
sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null

cd drake-ros
yes | sudo ./bazel_ros2_rules/setup/install_prereqs.sh
yes | sudo ./drake_ros_examples/setup/install_prereqs.sh
yes | sudo ./ros2_example_bazel_installed/setup/install_prereqs.sh

# Build workspaces
cd drake_ros
bazel build //...
bazel test //...

cd ..
cd ros2_example_bazel_installed
bazel build //...
bazel test //...

cd ..
cd drake_ros_examples
bazel build //...
bazel test //...