Default param values should be retained with @param

[devongovett]

When using default parameters in JS/Flow, but using @param to provide param descriptions, the default value is lost.

// @flow
/**
 * @param bar This is the bar parameter
 */
function foo(bar: string = 'foo') {
  
}

This can be "fixed" by repeating the default as part of the JSDoc comment.

// @flow
/**
 * @param [bar='foo'] This is the bar parameter
 */
function foo(bar: string = 'foo') {
  
}

This is annoying however. It would be nice if the default value inferred from the function declaration could be merged with the description provided by JSDoc. Alternatively, if there were a way to provide only the description to @param and not the name, that would work too, but this doesn't seem possible in the JSDoc spec.