[doc] @nest with several rules/selectors

[brillout]

From reading the doc I was expecting following to work

div {
  @nest .c1 &,
  @nest .c2 & {
    color: red;
  }
}

but the correct usage is

div {
  @nest
  .c1 &,
  .c2 & {
    color: red;
  }
}

A note or example about that would have saved me 30mn.

Thanks for postcss-cssnext btw, I really like it.

(cross issue: csstools/postcss-nesting#22)

[MoOx]

You are right, we should add this as an example.

[MoOx]

postcss-cssnext has been deprecated in favor of postcss-preset-env. Read more at https://moox.io/blog/deprecating-cssnext/