"""Load question-answer pairs from a benchmark CSV file.

The function reads a CSV file where each row contains a 'question' and 'answer' column. It strips any leading or trailing whitespace from both the question and answer, and stores them as key-value pairs in a dictionary.

Args:
    benchmark_file (str): Path to the CSV file containing the benchmark data.

Returns:
    dict: A dictionary where keys are questions and values are their corresponding answers.
"""
You should write code starting with:
import csv

def load_benchmark_data(benchmark_file: str) -> dict:
    # TODO: Implement this function
    pass

