add chromedriver flags via environment variable

[luroc]

Thanks for your work, already very usable for me.

It would be great to be able to customize the chromedriver execution.

In my case I wanted to add the '--hide-scrollbars' flag.
I added it to main.rs and recompiled and it works, but it would be nice to be able to set this e.g. via an environment variable.

[jzeuzs]

--hide-scrollbars is now enabled by default