feat(options): allow users to pass their own cleanCss Options (#377)

Author: alan-agius4

src/cleancss.ts

@@ -33,7 +33,7 @@ export function cleancssWorker(context: BuildContext, configFile: string): Promi
  Logger.debug(`cleancss read: ${srcFile}`);
 
  readFileAsync(srcFile).then(fileContent => {
- const minifier = new cleanCss();
+ const minifier = new cleanCss(cleanCssConfig.options);
  minifier.minify(fileContent, (err, minified) => {
  if (err) {
  reject(new BuildError(err));
@@ -72,5 +72,6 @@ export interface CleanCssConfig {
  sourceFileName: string;
  // sourceSourceMapName: string;
  destFileName: string;
- // destSourceMapName: string;
+ // options: cleanCss Options;
+ options?: cleanCss.Options;
 }