Improve JSDoc typings for optional parameters

[daniellockyer]

Hi! Love dockerode 😀

One thing I've noticed is that the JSDoc types for parameters which are optional aren't marked as so, so my editor tends to complain when I use dockerode with no params and Promises. Optional parameters in JSDoc are indicated with square brackets.

For example, container.inspect allows for optional opts and callback:

dockerode/lib/container.js

Lines 41 to 46 in bb88194

	/**
	* Inspect
	* @param {Object} opts Options (optional)
	* @param {Function} callback Callback, if supplied will query Docker.
	* @return {Object} ID only and only if callback isn't supplied.
	*/

In this example, the parameter types should be:

* @param  {Object}   [opts]     Options
* @param  {Function} [callback] Callback