add links to enter / exit folders

Reviewed-on: sites/file-explorer#5

src/Service/FileSystemService.php

@@ -20,10 +20,10 @@ class FileSystemService
     /**
      * @return DirContent[]
      */
-    public function getDirs(): array
+    public function getDirs(string $dirs): array
     {
         $finder = new Finder();
-        $finder->in($this->dir);
+        $finder->in($this->dir . '/' . $dirs);
 
         $contents = [];