Allow favoring your own posts from the post page

Just a small thing that confused me a bit: current behavior on https://github.com/gothinkster/vue-realworld-example-app and https://github.com/gothinkster/react-redux-realworld-example-app :

• you cannot favorite your own post from the post page, e.g. http://localhost:4101/article/zxcv-v4f34g The favorite button is replaced with the Delete button
• but you can favorite your own post from the global post index e.g. http://localhost:4101/

It is a bit weird to only be able to do it from one place but not the other, I'd just add the button favorite button in addition to the delete button.

Also:

• backends likely don't forbid favoriting self, so neither should frontend
• you are unable to see how many favorites your own post has while logged in, since that is shown on the button itself