Duplicated jsdoc should error

It's possible to document parameters and function expressions 2-3 different places in JSDoc. However, I can't think of a good reason to do so, and I suspect that it's (1) rare (2) by mistake. Here's an example: ```ts /** @param a - the a */ function f(/* an a */ a) { } ``` Today gives the jsdoc ``` an a - the a ``` But should give ` an a` and an error on `@param a`: "Duplicate jsdoc". The problem is even worse in JS, where jsdoc provides types. Here, the innermost type annotation provides the type and the rest are ignored. This should *definitely* be an error: ```js /** @param {string} a */ function f(/* @type {number} */ a) { } ``` This example should have an error on `@param a`: "Duplicate jsdoc" Thanks to @bterlson for this idea.