Sort by oldest

**Is your feature request related to a problem? Please describe.**
I am currently using "New". But when there are duplicated posts, I upvote the newer one post because I don't not yet know the older one. So I prefer the posts are sorted by oldest, so I read posts chronically.

**Describe the solution you'd like**
Adds a new "sort by oldest" option.

**Describe alternatives you've considered**
Using "New", go to bottom, and scrolling up? I think it is hard to do it daily.