fix: parse minimized css import

[ahabhgk]

fix case @import "./style.css";body{}

before:

.class-in-style-css{};

ody{}

after:

.class-in-style-css{};

body{}

there are some new lines introduced in the snapshot, because before the new line is removed unexpectedly:

before:

@import "./style.css";\n\nbody{}
//                      second \n: the removed new line
//                    first \n: end + 1

after:

@import "./style.css";\n\nbody{}
//                      second \n: keep it as is
//                    first \n: the removed new line

What kind of change does this PR introduce?

bugfix

Did you add tests for your changes?

added

Does this PR introduce a breaking change?

no

What needs to be documented once your changes are merged?

none

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)