Support for type declarations in JSDoc comments in vals.

[zarutian]

It would be much nicer if val.town supported the TypeScript extension of JSDoc were one can declare types and such.

It looks like val.town does it for imported stuff but not for the vals themselvs.

My personal preference is to use vanilla ecmascript but with type hints via aforesaid extended jsdoc comments.

(Plus parsers such as acorn.js or esma and escope do not parse ts cleanly yet and stuffing ts code through the transpiler first gives... curious results)