Add Contribute section to readme.md

Author: wooorm

readme.md

@@ -21,6 +21,20 @@ Oh, and [plug-ins][plugins]?!
 
 [Get started »][getting-started]
 
+## Contribute
+
+**remark** is built by people just like you!  Check out
+[`contribute.md`][contribute] for ways to get started.
+
+This project has a [Code of Conduct][coc].  By interacting with this repository,
+organisation, or community you agree to abide by its terms.
+
+Want to chat with the community and contributors?  Join us in [Gitter][chat]!
+
+Have an idea for a cool new utility or tool?  That’s great!  If you want
+feedback, help, or just to share it with the world you can do so by creating
+an issue in the [`remarkjs/ideas`][ideas] repository!
+
 ## License
 
 [MIT](LICENSE) © [Titus Wormer](http://wooorm.com)
@@ -60,3 +74,9 @@ Oh, and [plug-ins][plugins]?!
 [unified]: https://github.com/unifiedjs/unified
 
 [website]: https://unifiedjs.github.io
+
+[contribute]: contributing.md
+
+[coc]: code-of-conduct.md
+
+[ideas]: https://github.com/remarkjs/ideas