Disable javascript option & proxy url

[Niall47]

Adding new browser configurations for disabling javascript and setting proxy urls.
This allows you to register multiple variations of a browser that your tests can swap to without re-registering.

╰─➤  ./bin/console 
irb(main):001> DVLA::Browser::Drivers.selenium_firefox
Driver set to: 'selenium_firefox'
=> :selenium_firefox

irb(main):002> DVLA::Browser::Drivers.headless_selenium_firefox
Driver set to: 'headless_selenium_firefox'
=> :headless_selenium_firefox

irb(main):003> DVLA::Browser::Drivers.selenium_firefox_no_js
Driver set to: 'selenium_firefox_no_js'
=> :selenium_firefox_no_js

irb(main):004> DVLA::Browser::Drivers.headless_selenium_firefox_no_js
Driver set to: 'headless_selenium_firefox_no_js'
=> :headless_selenium_firefox_no_js

irb(main):005> Capybara.drivers.map(&:first)
=> 
[:rack_test,
 :selenium,
 :selenium_headless,
 :selenium_chrome,
 :selenium_chrome_headless,
 :apparition,
 :cuprite,
 :selenium_firefox,
 :headless_selenium_firefox,
 :selenium_firefox_no_js,
 :headless_selenium_firefox_no_js]