Support parsing TSDoc string comments

Hi there!

I had a issue trip around Github and finally ended up here :)

Last issue was: https://github.com/microsoft/vscode/issues/95408

I am using String Literal types to define classnames and would love to populate with some more information.

So basically:

type TClassnames = 
   /** Some docs about red-500 */
    | 'bg-color-red-500'
   /** Some docs about red-600 */
    | 'bg-color-red-600'

I would expect it to populate the docs on the right side of the intellisense:

This is how we can document with properties:

Which would be amazing to have on string literals.

I thought it was a TSDoc issue, but given this context: https://github.com/microsoft/tsdoc/issues/164, it seems to be VSCode not parsing it... though then it seems to actually be Typescript related?

The issue does not name files or tests; start by tracing TypeScript's language-service completion details for string-literal union members and compare the existing property documentation behavior. Done means TSDoc comments attached to individual string literals appear in IntelliSense, with coverage for the demonstrated union pattern.