feh(1): make config file names clearer

man/feh.pre

@@ -850,7 +850,8 @@ Note that mid-line comments are not supported.
 .
 .Sh THEMES CONFIG SYNTAX
 .
-This file allows the naming of option groups, called themes.
+.Pa .config/feh/themes
+allows the naming of option groups, called themes.
 .
 .Pp
 .
@@ -898,7 +899,9 @@ You can combine these themes with commandline options.
 .
 .Sh KEYS CONFIG SYNTAX
 .
-This file defines the key bindings. It has entries of the form
+.Pa .config/feh/keys
+defines key bindings.
+It has entries of the form
 .Qq Ar action Op Ar key1 Op Ar key2 Op Ar key3 .
 .
 .Pp
@@ -1195,6 +1198,7 @@ Select highlighted menu item
 .
 .Sh BUTTONS CONFIG SYNTAX
 .
+.Pa .config/feh/buttons .
 This works like the keys config file: the entries are of the form
 .Qq Ar action Op Ar binding .
 .