Expose API for getting JSDoc nodes in TypeScript files

Closure adds various semantic JSDoc annotations that aren't currently modeled by TypeScript, such as @export (unrelated to TS export) and @nosideeffects.
https://developers.google.com/closure/compiler/docs/js-for-compiler#overview

As part of our tool chain to run TypeScript through Closure we'd like to be able to munge these via the TypeScript API. It appears TypeScript gathers JSDoc comments when parsing JavaScript -- is there a good reason to not gather these in TypeScript as well?

Specifically, I believe my suggestion amounts to removing the "if" statement in the below code (though I'm not certain this is the right place) in parser.ts:

        function addJSDocComment<T extends Node>(node: T): T {
            if (contextFlags & NodeFlags.JavaScriptFile) {
                ...all of the code is in here...
            }
        }

Inizia in parser.ts, in addJSDocComment, e analizza come la guardia NodeFlags.JavaScriptFile limiti la raccolta di JSDoc. Confronta il percorso di parsing JavaScript esistente con il parsing dei file TypeScript e consulta la discussione dell’issue per verificare il confine API previsto. Il lavoro è completo quando i nodi JSDoc dei file TypeScript sono accessibili tramite l’API TypeScript, incluse le annotazioni Closure come @export e @nosideeffects.