Support URLs for custom filesystem drivers (#23964)

Some custom filesystem drivers don’t include URL support at the adapter level, but can be added to the driver through the creation of custom plugins. Applications can detect the plugin, but the Filesystem framework currently neglects to check for the ‘getUrl’ method on the driver level.

src/Illuminate/Filesystem/FilesystemAdapter.php

@@ -379,6 +379,8 @@ public function url($path)
 
         if (method_exists($adapter, 'getUrl')) {
             return $adapter->getUrl($path);
+        } elseif (method_exists($this->driver, 'getUrl')) {
+            return $this->driver->getUrl($path);
         } elseif ($adapter instanceof AwsS3Adapter) {
             return $this->getAwsUrl($adapter, $path);
         } elseif ($adapter instanceof RackspaceAdapter) {