Made a few small improvements

1. I added an alternative to the Windows folder browser dialog because I hate that dialog. You can hold down Control while clicking the Open Folder menu item to use a standard file open dialog, and it just uses the directory containing whichever file you selected. It won't interfere with the keyboard shortcut (Ctrl+Shift+O), as it won't do it if you're also holding Shift.

2. I also added a menu item to open the currently-selected directory in Explorer, a feature I thought was missing.