[New Feature] Support SAM 2.1 (#59)

* support sam 2.1

* refine config path and ckpt path

* update README

sam2/modeling/sam/mask_decoder.py

@@ -247,7 +247,7 @@ class MaskDecoder(nn.Module):
     def _get_stability_scores(self, mask_logits):
         """
         Compute stability scores of the mask logits based on the IoU between upper and
-        lower thresholds, similar to https://github.com/fairinternal/onevision/pull/568.
+        lower thresholds.
         """
         mask_logits = mask_logits.flatten(-2)
         stability_delta = self.dynamic_multimask_stability_delta