Add two-pane support to link posts

[mkatsevVR]

Right now if I open a self-post in a landscape tablet mode, it opens in the right column, while the left column shows the list of posts in a subreddit. However, if I open the link post, it opens fullscreen. hiding the list of posts. It makes it slower to switch between posts and harder to browse.

Suggestion: make an option to use the same display mode (two columns) for links, as for self-posts.