Install the side-by-side gz11/gz doc in the index and fix warning link (#444)

Signed-off-by: Jose Luis Rivero <[email protected]>

Author: j-rivero

garden/install_ubuntu.md

@@ -8,7 +8,7 @@ To install all of them, the metapackage `gz-garden` can be installed.
 WARNING: for gazebo-classic (eg. `gazebo11`) users: `gz-garden` cannot be
 installed alongside with `gazebo11` by default. To facilitate the migration
 this can be done using the instruction detailed in
-[Installing Gazebo11 side by side with new Gazebo](/docs/all/install_gz11_side_by_side).
+<a href="https://gazebosim.org/docs/garden/install_gz11_side_by_side">Installing Gazebo11 side by side with new Gazebo</a>
 </div>
 
 First install some necessary tools:

harmonic/install_ubuntu.md

@@ -8,7 +8,7 @@ To install all of them, the metapackage `gz-harmonic` can be installed.
 WARNING: for gazebo-classic (eg. `gazebo11`) users: `gz-harmonic` cannot be
 installed alongside with `gazebo11` by default. To facilitate the migration
 this can be done using the instruction detailed in
-[Installing Gazebo11 side by side with new Gazebo](/docs/all/install_gz11_side_by_side).
+<a href="https://gazebosim.org/docs/harmonic/install_gz11_side_by_side">Installing Gazebo11 side by side with new Gazebo</a>
 </div>
 
 First install some necessary tools:

index.yaml

@@ -22,12 +22,16 @@ pages:
   - name: ros_installation
     title: ROS/Gazebo Installation
     file: ros_installation.md
-    description: Our development plans.
+    description: Ros and Gazebo options and combinations
     children:
       - name: ros2_gz_vendor_pkgs
         title: ROS 2 Gazebo Vendor Packages
         file: ros2_gz_vendor_pkgs.md
         description: Using ROS 2 Gazebo Vendor packages
+  - name: install_gz11_side_by_side
+    title: Installing Gazebo11 side by side with new Gazebo
+    file: install_gz11_side_by_side.md
+    description: How to install gazebo11 and new Gazebo together
   - name: migrating_gazebo_classic_ros2_packages
     title: Migration from ROS 2 Gazebo Classic
     file: migrating_gazebo_classic_ros2_packages.md