Applications > Transmit.app.
You'll need to be connected to a server to access the full View context menu mentioned below. Any server will do.
With the Transmit window active, navigate to
View > Show Hidden Files. After selecting this menu item, invisible files are now shown in Transmit!
You're all done.
This guide shows you how to show hidden system files (e.g. .htaccess) in Finder by default.