energy-management-app: Add Water Heater in Readme index (project-chip#36344)

* energy-management-app: Add Water Heater in Readme index

energy-management-app: Add Water Heater in Readme index

* Restyle

Author: lboue

examples/energy-management-app/linux/README.md

@@ -24,6 +24,7 @@ details.
         -   [Activating python virtual env](#activating-python-virtual-env)
         -   [Interacting with CHIP-REPL and the example app](#interacting-with-chip-repl-and-the-example-app)
         -   [Using chip-repl to Fake a charging session](#using-chip-repl-to-fake-a-charging-session)
+    -   [Water Heater App: Interaction using the chip-tool and TestEventTriggers](#water-heater-app-interaction-using-the-chip-tool-and-testeventtriggers)
 
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