windows/dir: update page (#10913)

* windows: dir: add "bare" format

Add "dir /B" to the cheat sheet. It is quite useful for creating file
lists, playlists and the like, without having to manually mangle the
output.

* Change parameters to lowercase and reword description

pages/windows/dir.md

@@ -13,8 +13,12 @@
 
 - Show the contents of the current directory, including hidden ones:
 
-`dir /A`
+`dir /a`
 
 - Show the contents of a given directory, including hidden ones:
 
-`dir {{path\to\directory}} /A`
+`dir {{path\to\directory}} /a`
+
+- Show a bare list of directories and files, with no additional information:
+
+`dir /b`