Feature: Log files (#423)

* log_file

feature: added a new parameter for crew that creates a txt file to log agent execution

* unit tests and documentation

unit test if file is created but not what is inside the file

src/crewai/utilities/__init__.py

@@ -5,3 +5,4 @@ from .logger import Logger
 from .printer import Printer
 from .prompts import Prompts
 from .rpm_controller import RPMController
+from .fileHandler import FileHandler