Implemented the culture delete function

I18N Commander/Processor/AppSettings.cs

@@ -385,6 +385,29 @@ public static class AppSettings
     
     #endregion
 
+    #region Delete a culture
+    
+    public static async Task DeleteCulture(int index)
+    {
+        // Get the database:
+        await using var db = ProcessorMeta.ServiceProvider.GetRequiredService<DataContext>();
+        
+        // Check, if the setting is already set:
+        if (await db.Settings.FirstOrDefaultAsync(n => n.Code.StartsWith(SettingNames.CULTURE) && n.IntegerValue == index) is {} existingSetting)
+        {
+            db.Settings.Remove(existingSetting);
+            await db.SaveChangesAsync();
+        }
+        
+        // Update the list of cultures indices:
+        CACHE_CULTURES_INDICES.Remove(index);
+
+        // Update the cache:
+        CACHE_CULTURES.Remove(index);
+    }
+
+    #endregion
+
     #region Get a list of cultures
 
     public readonly record struct CultureInfo(string Code, int Index);