Add warning sign for early development

Summary: Clarify expectations around early development and reporting bugs.

Reviewed By: jspisak

Differential Revision: D75032118

fbshipit-source-id: 9644503d4474475d016967a72efc7bb4b4096919

Author: dcci

README.md

@@ -1,8 +1,11 @@
-# Getting started
+# Monarch
 
-## Installation
+**Monarch** is a distributed execution engine for PyTorch.
+
+> ⚠️ **Early Development Warning**
+> Monarch is currently in an experimental stage. You should expect bugs, incomplete features, and APIs that may change in future versions. The project welcomes bugfixes, but to make sure things are well coordinated you should discuss any significant change before starting the work. It's recommended that you signal your intention to contribute in the issue tracker, either by filing a new issue or by claiming an existing one.
 
-TODO improve
+## Installation
 
 ```sh