"Go to File..." search can now filter files based on the workspace folder name.

This feature is activated only when the workspace contains more than one folder.

This is particularly useful when your workspace contains multiple files with the same name, each of them in another workspace folder.

A common example is the `README.md` file. Say you want to find a `README.md` file from a particular folder, say `my-folder`. Before this change you'd have to press the `Down` button a few times before you could get to the file.

With this change you'd instead search for `mfREADME.md`. The desired readme file should now appear closer to the top of the file search popup.