Use diplodoc/themes for css tokens

We need to use [diplodoc/themes](https://github.com/diplodoc-platform/themes) library for configure css tokens in this repo. In this place for example https://github.com/diplodoc-platform/openapi-extension/blob/master/src/runtime/index.scss#L4-L15

and also we need to extracts variables in diplodoc/themes library and use these variables from library

and in this repository, we need to create building scss files after the build, otherwise the colors won't be replaced when we want to override them in other applications