给selenium自定义user-agent

给selenium自定义user-agent。分别给firefox driver和chromedriver自定义user-agent的示例方法：

示例1：

from selenium import webdriver

profile = webdriver.FirefoxProfile()

profile.set_preference("general.useragent.override", "whatever you want")

driver = webdriver.Firefox(profile)

示例2：

from selenium import webdriver

from selenium.webdriver.chrome.options import Options

opts = Options()

opts.add_argument("user-agent=whatever you want")

driver = webdriver.Chrome(chrome_options=opts)

检测显示当前user-agent

agent = driver.execute_script("return navigator.userAgent")