Fix missing imports

Add missing imports for `Tool` and `Function`

README.md

@@ -12,6 +12,10 @@ from mistral_common.protocol.instruct.messages import (
     AssistantMessage,
     UserMessage,
 )
+from mistral_common.protocol.instruct.tool_calls import (
+    Tool,
+    Function,
+)
 from mistral_common.tokens.tokenizers.mistral import MistralTokenizer
 from mistral_common.tokens.instruct.normalize import ChatCompletionRequest