[dash] Show fragment count with --live-from-start (#3493)

Authored by: flashdagger

yt_dlp/downloader/dash.py

@@ -73,6 +73,7 @@ class DashSegmentsFD(FragmentFD):
 
             yield {
                 'frag_index': frag_index,
+                'fragment_count': fragment.get('fragment_count'),
                 'index': i,
                 'url': fragment_url,
             }