fix: correctly parse the directory of a given path to a file

The previous `gsub` call would blow away everything after and including
the first '/' in the pathname, including other slashes.

Fortunately, the neovim api provides a way to get the parent directory
of a given path, which I've used instead.

lua/genghis.lua

@@ -96,7 +96,7 @@ local function fileOp(op)
 		-- DETERMINE PATH AND EXTENSION
 		local hasPath = newName:find("/")
 		if hasPath then
-			local newFolder = newName:gsub("/.-$", "")
+ 			local newFolder = vim.fs.dirname(newName)
 			fn.mkdir(newFolder, "p") -- create folders if necessary
 		end