Option for http authentication

[pdaether]

I'm using minimalcss on a staging system which is protected with a basic http authentication.
At the moment this only works with minimalcss when giving the credentials as part of the URL wich is not perfect, because then you have the password in different logs.
It would be nice if it would be possible to give username and password as part of the options so that minimalcss can set the credentials on the puppeteer page object.

I know that I can pass a puppeteer browser instance, but the the credentials need to be given to the page object, so I guess best place would be somewhere in src/run.js

const page = await browser.newPage();
await page.authenticate({'username':options.auth.username, 'password': options.auth.password});

If you agree on a general approach, I'm also happy to provide a PR.

[peterbe]

If you agree on a general approach, I'm also happy to provide a PR.

Please go for it! Yay!