Fixed deprecated autoprefixer config warning when running build tasks

no issue

Passing browser options directly into `autoprefixer()` has been deprecated in favour of general browserslist configuration in `package.json` or a `.browserslistrc` config file

- moved autoprefixer browsers list into `browserslist` config in `package.json`
- updated `autoprefixer` version

gulpfile.js

@@ -43,7 +43,7 @@ function css(done) {
         easyimport,
         customProperties({preserve: false}),
         colorFunction(),
-        autoprefixer({browsers: ['last 2 versions']}),
+        autoprefixer(),
         cssnano()
     ];