feat(l10n): add searchingFor string for Arabic and English

- Add new string for loading state on search page
- Include string in both Arabic (app_ar.arb) and English (app_en.arb) localization files
- Use placeholder for content type

Author: fulleni

lib/l10n/app_localizations.dart

@@ -1519,6 +1519,12 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'Countries'**
   String get contentTypeCountry;
+
+  /// Subheadline for loading state on search page
+  ///
+  /// In en, this message translates to:
+  /// **'Searching for {contentType}...'**
+  String searchingFor(String contentType);
 }
 
 class _AppLocalizationsDelegate

lib/l10n/app_localizations_ar.dart

@@ -785,4 +785,9 @@ class AppLocalizationsAr extends AppLocalizations {
 
   @override
   String get contentTypeCountry => 'الدول';
+
+  @override
+  String searchingFor(String contentType) {
+    return 'جار البحث عن $contentType...';
+  }
 }

lib/l10n/app_localizations_en.dart

@@ -785,4 +785,9 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get contentTypeCountry => 'Countries';
+
+  @override
+  String searchingFor(String contentType) {
+    return 'Searching for $contentType...';
+  }
 }

lib/l10n/arb/app_ar.arb

@@ -1005,5 +1005,14 @@
     "contentTypeCountry": "الدول",
     "@contentTypeCountry": {
         "description": "Label for Country content type"
+    },
+    "searchingFor": "جار البحث عن {contentType}...",
+    "@searchingFor": {
+        "description": "Subheadline for loading state on search page",
+        "placeholders": {
+            "contentType": {
+                "type": "String"
+            }
+        }
     }
 }

lib/l10n/arb/app_en.arb

@@ -1021,5 +1021,14 @@
     "contentTypeCountry": "Countries",
     "@contentTypeCountry": {
         "description": "Label for Country content type"
+    },
+    "searchingFor": "Searching for {contentType}...",
+    "@searchingFor": {
+        "description": "Subheadline for loading state on search page",
+        "placeholders": {
+            "contentType": {
+                "type": "String"
+            }
+        }
     }
 }