Update examples in README to be compatible with soon-to-come ChatWidget (#2)

- Update examples in README to be compatible with soon-to-come ChatWidget (c0a423e725a422bc31c83697d77c8bba775e5f0b)
- Update README.md (98c5586ece54a5a0f6be44c9efc2a1fcbcdffde6)


Co-authored-by: Lucain Pouget <Wauplin@users.noreply.huggingface.co>

README.md

@@ -19,7 +19,9 @@ datasets:
 - HuggingFaceH4/ultrachat_200k
 - meta-math/MetaMathQA
 widget:
-- text: "<|prompt|>Why is drinking water so healthy?</s><|answer|>"
+- messages:
+  - role: user
+    content: Why is drinking water so healthy?
 ---
 # Model Card
 ## Summary