docs: function buildCSS(src, filename, dest, applyHeader) {
    dest = dest || config.dist.cssPath;
    applyHeader = applyHeader || false;
  
    return gulp.src(src)
      .pipe(sass({
        includePaths: [config.src.scssPath, config.packagesPath]
      })
        .on('error', sass.logError))
      .pipe(cleanCSS())
      .pipe(autoprefixer({
        // Supported browsers added in package.json ("browserslist")
        cascade: false
      }))
      .pipe(gulpif(applyHeader, header(config.prj.header, {
        config: config
      })))
      // Remove charset rule (if present) and add to the first
      // line of the stylesheet (@charset must be on the first line)
      .pipe(replace('@charset "UTF-8";', ''))
      .pipe(header('@charset "UTF-8";\n'))
      .pipe(rename(filename))
      .pipe(gulp.dest(dest));
  }