Add an original link at bottom/top when publish to matters

[jackysee]

When publish to matters, it would be nice to have an original link at the bottom of the article. e.g. (原文刊於<a href="xxx">XXX</a>). The link would be the permalink of the article and the text would be the name of blog.

[williamchong]

Good idea, will implement this when I have time.
A PR would also be welcomed.

[williamchong]

Added in #83