fix: add about to drawer

lib/util/drawer.dart

@@ -62,6 +62,22 @@ Drawer genDrawer(int page, BuildContext context) => Drawer(
                     ),
                   ),
           ),
+          ListTile(
+            selected: page == 3,
+            title: const Text("About"),
+            leading: const Icon(Icons.info_outline),
+            onTap: () => page == 3
+                ? Navigator.of(context).pop()
+                : Navigator.of(context).push(
+                    MaterialPageRoute(
+                      builder: (_) => const LicensePage(
+                        applicationName: "Voyage Handbook",
+                        applicationLegalese:
+                            "Copyright ©️ 2023 Matyáš Caras,\nReleased under the GNU GPL version 3",
+                      ),
+                    ),
+                  ),
+          ),
         ],
       ),
     );