create .gitignore file in video download folder

pipeline/download_videos.py

@@ -17,7 +17,7 @@ def get_id(url: str) -> str:
 
 def download_videos(video_ids: List[str]) -> None:
     VIDEO_DIR.mkdir(exist_ok=True, parents=True)
-    (VIDEO_DIR / "gitignore").write_text("*")
+    (VIDEO_DIR / ".gitignore").write_text("*")
     for video_id in tqdm(video_ids):
         video_url = f"https://www.youtube.com/watch?v={video_id}"
         video_path = VIDEO_DIR / f"{video_id}.mp4"