[DX] Apply cssrewrite to css, sass and less files by default

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #670
| License       | MIT
| Doc PR        | -

Tweked the configuration to apply cssrewrite to css, sass and less files by default