Resolve selectors using AST of language service

[Viijay-Kr]

During the investigation of #18 , it's quite evident that the selectors resolution namely the suffix selectors resolution doesn't seem to be 100% bullet proof.

It encounters various issues besides the conflicting names with other selectors in the module.

Approach 1

Custom Tree traversal Algorithm

With the AST available (generated by vcode-css-langaugeservice) it should be possible to create an algorithm that traverses the AST and computes the nested selectors on every entry.

So on start up , a custom data structure that can hold the following information

1. Selector
2. Sibling Selectors
3. Child Selectors: [Suffixes,Normal Selectors]
   in one single HashMap would be ideal and quick for resolution inside the tsx modules.

Challenges

To traverse the AST, there is no function/utility provided by vscode-language-service
Ideally a traverse mechanism should be written from scratch , that should also include type definitions.