Updated Contribution guide (markdown)

Contribution-guide.md

@@ -1,6 +1,6 @@
 **Don't use Docker to do development**. It's a quick way to get Mastodon running in production, it's **really really inconvenient for development**. Normally in Rails development environment you get hot reloading of backend code and on-the-fly compilation of assets like JS and CSS, but you lose those benefits by compiling a Docker image. If you want to contribute to Mastodon, it is worth it to simply set up a proper development environment.
 
-In fact, all you need is described in the production guide, **with the following exceptions**. You **don't** need:
+In fact, all you need is described in the [production guide](https://github.com/Gargron/mastodon/wiki/Production-guide), **with the following exceptions**. You **don't** need:
 
 - Nginx
 - SystemD