Add bot prefix modifier option in extensions

extensions/example/script.py

@@ -1,5 +1,6 @@
 params = {
     "input suffix": " *I say as I make a funny face*",
+    "bot prefix": " *I speak in a cute way*",
 }
 
 def input_modifier(string):
@@ -16,3 +17,12 @@ def output_modifier(string):
     """
 
     return string
+
+def bot_prefix_modifier(string):
+    """
+    This function is only applied in chat mode. It modifies
+    the prefix text for the Bot and can be used to bias its
+    behavior.
+    """
+
+    return string + params["bot prefix"]