style: Moved argument parsing statements into a separate function

[aravindsomaraj]

I just made a minor change in main.py by moving these lines into a separate function parse_arguments(), and having it be called from main(). I think it would improve readability a bit.
Lines in question:

parser = argparse.ArgumentParser(description="Run an agent with a specific task")
parser.add_argument("-d", "--directory", required=True, type=str, help="The working directory for the agent")
parser.add_argument("-t", "--task", type=str, default="", help="The task for the agent to perform")
parser.add_argument("-f", "--file", type=str, help="Path to a file containing the task. Overrides -t if both are provided.")
parser.add_argument("-c", "--agent-cls", default="LangchainsAgent", type=str, help="The agent class to use")
parser.add_argument("-m", "--model-name", default=config.get_or_default("LLM_MODEL", "gpt-4-0125-preview"), type=str, help="The (litellm) model name to use")
parser.add_argument("-i", "--max-iterations", default=100, type=int, help="The maximum number of iterations to run the agent")