Update controls in docs and other files

rtv/docs.py

@@ -34,6 +34,7 @@ HELP = """
   `d`                 : Delete an existing post or comment
   `i`                 : Display new messages prompt
   `s`                 : Open/close subscribed subreddits list
+  `S`                 : Open/close subscribed multireddits list
 
 [Subreddit Mode]
   `l` or `RIGHT`      : Enter the selected submission

rtv/rtv.cfg

@@ -125,4 +125,4 @@ MULTIREDDIT_OPEN_SUBSCRIPTIONS = S
 
 ; Subscription page
 SUBSCRIPTION_SELECT = l, <LF>, <KEY_ENTER>, <KEY_RIGHT>
-SUBSCRIPTION_EXIT = h, s, <ESC>, <KEY_LEFT>
+SUBSCRIPTION_EXIT = h, s, S, <ESC>, <KEY_LEFT>