Update examples/platform/silabs/BaseApplication.h

Co-authored-by: Mathieu Kardous <84793247+mkardous-silabs@users.noreply.github.com>

Author: lpbeliveau-silabs

examples/platform/silabs/BaseApplication.h

@@ -177,7 +177,10 @@ class BaseApplication
 protected:
     CHIP_ERROR Init();
     CHIP_ERROR BaseInit();
-    virtual CHIP_ERROR AppInit() { return CHIP_NO_ERROR; }
+   /** @brief Template for to implement a Application specific init. 
+      *              Function is called after the BaseApplication::Init function.
+     */
+    virtual CHIP_ERROR AppInit() = 0;
 
     /**
      * @brief Function called to start the function timer