3056065: Added the external CSS library version.

Closes #3056065

core/lib/Drupal/Core/Asset/CssCollectionRenderer.php

@@ -55,8 +55,11 @@ public function render(array $css_assets) {
           // Only add the cache-busting query string if this isn't an aggregate
           // file.
           if (!isset($css_asset['preprocessed'])) {
+            $version_query_string = (!empty($css_asset['version']) && $css_asset['version'] !== -1)
+            ? 'v=' . $css_asset['version']
+            : $query_string;
             $query_string_separator = str_contains($css_asset['data'], '?') ? '&' : '?';
-            $element['#attributes']['href'] .= $query_string_separator . $query_string;
+            $element['#attributes']['href'] .= $query_string_separator . $version_query_string;
           }
           break;