Add warning in status widget when debug mode is enabled (#4500)

Debug mode is now shown as a warning in the Status report widget to indicate that its use is discouraged for production websites.

Credit to @Samuell1.

modules/backend/lang/en/lang.php

@@ -364,6 +364,7 @@ return [
         'permissions'  => 'Directory :name or its subdirectories is not writable for PHP. Please set corresponding permissions for the webserver on this directory.',
         'extension' => 'The PHP extension :name is not installed. Please install this library and activate the extension.',
         'plugin_missing' => 'The plugin :name is a dependency but is not installed. Please install this plugin.',
+        'debug' => 'Debug mode is enabled. This is not recommended for production installations.'
     ],
     'editor' => [
         'menu_label' => 'Editor settings',

modules/system/reportwidgets/Status.php

@@ -99,6 +99,10 @@ class Status extends ReportWidgetBase
             $writablePaths[] = themes_path();
         }
 
+        if (Config::get('app.debug', true)) {
+            $warnings[] = Lang::get('backend::lang.warnings.debug');
+        }
+
         $requiredExtensions = [
             'GD'       => extension_loaded('gd'),
             'fileinfo' => extension_loaded('fileinfo'),