Add new syntax

[kartofelek007]

On page:
https://www.npmjs.com/package/gulp-autoprefixer
there is old syntax. Parameter "browsers" in depreaced and task syntax is for gulp 3.9.

On gulp 4.0 you must use syntax like that:

const css = function() {
     return gulp.src('src/app.css')
        .pipe(autoprefixer({
            cascade: false
        }))
        .pipe(gulp.dest('dist'));
}

According to browserlist instruction, parameter "browser" must be change to correct info:
https://github.com/browserslist/browserslist

This should be in instruction.