Recommend subreddits based on what the user is already subscribed to
This currently uses subreddit similarity data from anvaka/sayit. To summarise, two subreddits are considered similar if the same people comment in boths. While not perfect, it is a decent approximation of similarity. Further work could include computing new similarity data which would be based on subscriptions, not commenters (i.e. subreddits are similar if they share a lot of subscribers).
- add manual input field instead of via Reddit oauth