Console warnings for missing translations on development builds

(cherry picked from commit 67a1ecb0fea4e6c7dfdb68fbe3ef30d4c22398d8)

Closes #5239

frontend/src/Utilities/String/translate.ts

@@ -27,6 +27,12 @@ export default function translate(
   key: string,
   tokens: Record<string, string | number | boolean> = {}
 ) {
+  const { isProduction = true } = window.Lidarr;
+
+  if (!isProduction && !(key in translations)) {
+    console.warn(`Missing translation for key: ${key}`);
+  }
+
   const translation = translations[key] || key;
 
   tokens.appName = 'Lidarr';

frontend/typings/Globals.d.ts

@@ -7,5 +7,6 @@ interface Window {
     theme: string;
     urlBase: string;
     version: string;
+    isProduction: boolean;
   };
 }