Add autoprefixer to webpack config

[yasharAyari]

Expected behaviour

We should have some browser prefixes for some css features.This lets us to have same styles in all modern browsers.

Actual behaviour

We don't have them in our current version.

Steps to reproduce

1. Add postcss autoprefixer plugin to the project.
2. Add autoprefixer to our postcss configs in webpack config file and it will automatically add browsers prefixes to our css files.