Added the option to change WebDriver capabilities

[huds2]

I had to change the default capabilities for the WebDriver but the crate does not provide this function.

Renamed the chrome() function to chrome_caps and made it accept ChromeCapabilities as an argument.

Also created a chrome() function that calls chrome_caps with default ChromeCapabilities.

Usage example (changing the downloads directory):

let mut caps = DesiredCapabilities::chrome();
let mut prefs = HashMap::new();
prefs.insert("download.default_directory", "/path/to/directory");
caps.add_chrome_option("prefs", prefs)?;
let driver = chrome_caps(caps).await?;

[Ulyssedev]

Thanks for the contribution! I still have lots of changes to merge and will try to have a look at it as soon as possible