[#27][Feat] Add support for Safe Parser

[phoenisx]

This is a big change, to support safe parsers. In future, this extension would have its own parser for CSS variables supporting any extension.

• Safe Parser triggers only for extensions whose parser is not provided.
• To get accurate parsed data, a syntax parser is still required.
  • I want to create a generic parser for CSS variables so that syntax parser dependency can be removed entirely.

This change is not breaking in nature.

Usage for safe parser may or may not work properly for unsupported extensions, like jsx, tsx, vue etc. Future updates will fix that.