feat: add fullscreen capability to window settings

Adds the "core:window:allow-set-fullscreen" capability to the 
default configuration. This change enables the application to 
support fullscreen mode, enhancing user experience and 
providing more flexibility in window management

src-tauri/capabilities/default.json

@@ -39,6 +39,7 @@
         "fs:default",
         "updater:default",
         "dialog:default",
-        "process:default"
+        "process:default",
+        "core:window:allow-set-fullscreen"
     ]
 }