`filter` parameter `fs.copy` and `fs.copySync` 

Both `fs.copy` and `fs.copySync` have a new parameter `filter` which behaves like a whitelist.

`filter` can be a function or a regular expression

* for filter:function, `filter(srcPath)` must be true for copy
* for filter:RegExp, `filter.test(srcPath)` must be true for copy