Add EOL information to README (#3404)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>

README.md

@@ -2,9 +2,11 @@ Gazebo - A dynamic multi-robot simulator
 ----------------------------------------
 ![image](https://user-images.githubusercontent.com/10261903/174557418-1a83fbb7-e12b-4edb-b99f-5aaf8eed5cae.png)
 
-> **Note**
->  ### A new version of Gazebo (formerly known as Ignition) is now available. Please visit https://gazebosim.org or https://github.com/gazebosim/gz-sim to learn more.
-
+> [!NOTE]
+> A new version of Gazebo (formerly known as Ignition) is now available. Please visit https://gazebosim.org or https://github.com/gazebosim/gz-sim to learn more.
+ 
+> [!WARNING]
+> ### Gazebo Classic will reach End-Of-Life in [January 2025](https://classic.gazebosim.org/#collapseVersion11_0). Users are highly encouraged to migrate to the new Gazebo using our [migration guides](https://gazebosim.org/docs/latest/gazebo_classic_migration/)
 
 This is the [Gazebo Classic](http://classic.gazebosim.org) simulator.  Gazebo simulates multiple robots in a
 3D environment, with extensive dynamic interaction between objects.