Design tokens improvement

[PKulkoRaccoonGang]

To make working with design tokens easier in the future, it would be great to add a few helpers:

1. Set up a linter to validate the formatting of files containing design tokens (tokens folder).

2. Script for checking CSS variables declaration.
   Previously, when using SCSS variables, if the SCSS variable was not declared but was used, we could see an error during assembly and fix this problem. When using CSS variables, if the variable is used in Paragon components and has been deleted, we will not know about it. Thus, the browser is the only tool for validating variable declarations, which is not very convenient.