beef up getting started (#8139)

Co-authored-by: Bagatur <baskaryan@gmail.com>

docs/snippets/get_started/quickstart/input_messages.mdx

@@ -0,0 +1,12 @@
+```python
+from langchain.schema import HumanMessage
+
+text = "What would be a good company name for a company that makes colorful socks?"
+messages = [HumanMessage(content=text)]
+
+llm.predict_messages(messages)
+# >> Feetful of Fun
+
+chat_model.predict_messages(messages)
+# >> Socks O'Color
+```