[New Feature] Support SAM 2.1 (#59)

* support sam 2.1

* refine config path and ckpt path

* update README

demo/backend/server/data/store.py

@@ -0,0 +1,28 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+# This source code is licensed under the license found in the
+# LICENSE file in the root directory of this source tree.
+
+from typing import Dict
+
+from data.data_types import Video
+
+ALL_VIDEOS: Dict[str, Video] = []
+
+
+def set_videos(videos: Dict[str, Video]) -> None:
+    """
+    Set the videos available in the backend. The data is kept in-memory, but a future change could replace the
+    in-memory storage with a database backend. This would also be more efficient when querying videos given a
+    dataset name etc.
+    """
+    global ALL_VIDEOS
+    ALL_VIDEOS = videos
+
+
+def get_videos() -> Dict[str, Video]:
+    """
+    Return the videos available in the backend.
+    """
+    global ALL_VIDEOS
+    return ALL_VIDEOS