Update README.md (#353)

Summary:
point to new code location in `torchao`

Pull Request resolved: #353

Reviewed By: msaroufim

Differential Revision: D60452586

Pulled By: vkuzo

fbshipit-source-id: 9bef1b6ac5ac0f7ebced7c5b986226cf9db6a5e2

Author: vkuzo

README.md

@@ -1,3 +1,10 @@
+# NOTICE: float8_experimental has moved
+
+We have moved `float8_experimental` to 
+[pytorch/ao](https://github.com/pytorch/ao/tree/main/torchao/float8)
+
+- `import float8_experimental` is now `import torchao.float8`
+
 # float8_experimental
 
 This is an early version of a library for accelerating training with float8 in native PyTorch