[New Feature] Support SAM 2.1 (#59)

* support sam 2.1

* refine config path and ckpt path

* update README

sam2/__init__.py

@@ -5,5 +5,7 @@
 # LICENSE file in the root directory of this source tree.
 
 from hydra import initialize_config_module
+from hydra.core.global_hydra import GlobalHydra
 
-initialize_config_module("sam2_configs", version_base="1.2")
+if not GlobalHydra.instance().is_initialized():
+    initialize_config_module("sam2", version_base="1.2")