Better display missing localizations

src/i18n.rs

@@ -86,7 +86,17 @@ pub fn i18n_filter(
         .unwrap_or_else(|| vec![DEFAULT]);
     for lang in langs {
         if let Some(catalog) = catalogs.get(lang) {
-            return Ok(Value::String(catalog.gettext(key).to_owned()));
+            return Ok(Value::String({
+                let mut value = catalog.gettext(key);
+                if value.is_empty() {
+                    value = key;
+                }
+                if value.eq(key) {
+                    format!("❓ {value} ❓")
+                } else {
+                    value.to_owned()
+                }
+            }));
         }
     }
     panic!("Missing catalog");