Use more customized main page for reddit

The / main page seems to be a bit too "dangerous", this should make it
easy to go to a particular subscribed subreddit without much
distraction.

dotfiles/bmo/uris.ini

     mbr     = https://musicbrainz.org/
     mfp     = http://musicforprogramming.net/
     ol      = http://www.openlmi.org/
-    rdt     = https://www.reddit.com/
+    rdt     = https://www.reddit.com/subreddits/
     so      = http://stackoverflow.com/
     tjc     = https://together.jolla.com/
     tor     = https://theoldreader.com/