Fix issue #642, frontend not in english if the user language does not exist (#648)

* syntax and names

* Solve the issue #642, by searching index of english language code in catalog.

plume-front/src/main.rs

@@ -46,10 +46,15 @@ lazy_static! {
         let catalogs = include_i18n!();
         let lang = js! { return navigator.language }.into_string().unwrap();
         let lang = lang.splitn(2, '-').next().unwrap_or("en");
+
+        let english_position = catalogs
+            .iter()
+            .position(|(language_code, _)| *language_code == "en")
+            .unwrap();
         catalogs
             .iter()
             .find(|(l, _)| l == &lang)
-            .unwrap_or(&catalogs[0])
+            .unwrap_or(&catalogs[english_position])
             .clone()
             .1
     };