[✨] feat: Add the option of pass plain css

[TheElegantCoding]

Critical should have the option of only pass the css and avoid all the boilerplate

generate({
  rawCss: `html{display:block;}.someclass{color:red}`
}, (err, output) => {
    console.log(output)
});

expected output:

html{display:block;}

[bezoerb]

@TheElegantCoding from v7.1.0 on you should be able to also pass plain css to critical using the css option:

generate({
  css: `html{display:block;}.someclass{color:red}`
}, (err, output) => {
    console.log(output)
});

or via CLI:

critical http://my-domain.com -c 'html{display:block;}.someclass{color:red}'

[bezoerb]

please verify