feat: Add button to clear message history in chatbot

pages/chatbot.py

@@ -124,6 +124,10 @@ def page():
     # Models selector
     selector.ModelSelector()
 
+    if(len(st.session_state[chapter_session_key]["messages"]) > 1):
+        if st.button("Effacer l'historique"):
+            st.session_state[chapter_session_key]["messages"] = [ SystemMessage(content=chapterDB['prompt_system']) ]
+
     # Displaying messages
     display_messages()