Port our Graffiti Wall tutorial into this site

[asg017]

Project link: https://github.com/os-ucsd/graffiti-wall
Tutorial link: https://tinyurl.com/graffiti-wall-tutorial

Let's move the same contents in the dropbox paper doc (markdown, images, etc.) as a new post into this site.

[cqvu]

I got this issue!