feature request: add "edit" button

[ratnanil]

We would really welcome an "edit" button in distilll articles and blogposts, similar to what is available in bookdown.

edit : a link that collaborators can click to edit the Rmd source document of the current page; this was designed primarily for GitHub repositories, since it is easy to edit arbitrary plain-text files on GitHub even in other people’s repositories (if you do not have write access to the repository, GitHub will automatically fork it and let you submit a pull request after you finish editing the file).

Could something like this be implemented?

Disclaimer: I've asked if this was already implemented on community.rstudio.com, and Mara recommended filing a feature request.