Expose API to get the current CSTNode

[bd82]

Lets say we want to modify the CSTNode being created.

For Example:

        $.RULE("array", () => {
            const from = this.currIdx
           $.CONSUME(LSquare)
            // ...
            $.CONSUME(RSquare)
            const to = this.currIdx

            // Ugly way to access the current CSTNode using internal APIs
            this.CST_STACK[this.CST_STACK.length - 1].tokVectorRange = {
                from: from,
                to: to
            }
        })

It seems there should be a better way to access the current CSTNode.
Both in terms of being documented on the public API and in terms of conciseness.
Perhaps something like this.currCSTNode or maybe just this.currNode

[bd82]

Tasks

• Expose relevant method on the tree builder parser trait.
• Document the new API in api.d.ts CstParser class.
• Should there be special handling if this API is called from an EmbeddedActionsParser?
  - e.g throw an error?
• Tests and 100% Coverage.
• Create small example in examples/parser for this scenario.
• Update CST Guide Docs on the website (also link above example).

[bd82]

Thanks for helping @drayavannie, lets track everything in this single issue?