feat: add desktop capability schema with default permissions

src-tauri/capabilities/desktop.json

@@ -0,0 +1,11 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Default capability for all windows on desktop builds.",
+  "windows": ["*"],
+  "permissions": [
+    "core:default",
+    "shell:default",
+    "notification:default"
+  ]
+}