Feature Request - Make Symbol and AST publicly accessible

[vuquocbao]

Hello,

I'm wondering if you can make the AST tree from the parser publicly accessible outside of the module. I have a framework that uses graphQL to build out a JSON document and build a configuration framework that uses your library. I would like to be able to analyze the AST to determine what fields are needed so graphQL only resolved what is needed depending on the jsonata expressions. In addition, I have other uses to introspect the AST.

Right now the Symbol class is internal so I cannot access it