Update stylis.js dependency to v4

[vladshcherbin]

Describe the enhancement

Since 2.0 is coming, maybe it's not too late to update stylis.js dependency to v4.

Motivation

There might be improvements in different areas as well as breaking changes.

Possible implementations

Update stylis.js and hope tests pass 🙈

Related Issues

#582

[Anber]

I've found at least one small BC… 4.0 just doesn't have an API which we used :)
The repo also doesn't have a changelog or something similar, so I think, it's not safe to upgrade it right now.

[agriffis]

This might help: thysultan/stylis#213

[agriffis]

It looks like @ludofischer updated his fork to use stylis v4, see commit linked above.

I'd like to see this in linaria proper, especially because stylis v4 fixes bugs I care about:

stylis v3

> const stylis = require('stylis')
> stylis('', '.a { :is(.b) { color: green; } }')
'.a:is(.b){color:green;}'

stylis v4

> const {compile, serialize, stringify} = require('stylis')
> serialize(compile('.a { :is(.b) { color: green; } }'), stringify)
'.a :is(.b){color:green;}'

Note .a:is() versus .a :is(). To get the expected result on stylis v3, you need to constantly include * or & in places where you normally wouldn't need to in something like SASS.