Add Contribute section to readme.md

Author: wooorm

readme.md

@@ -74,6 +74,13 @@ example.md: no issues found
 
 Parse the tree again, also parsing “raw” nodes (as exposed by remark).
 
+## Contribute
+
+See [`contribute.md` in `rehypejs/rehype`][contribute] for ways to get started.
+
+This organisation has a [Code of Conduct][coc].  By interacting with this
+repository, organisation, or community you agree to abide by its terms.
+
 ## License
 
 [MIT][license] © [Titus Wormer][author]
@@ -95,3 +102,7 @@ Parse the tree again, also parsing “raw” nodes (as exposed by remark).
 [author]: http://wooorm.com
 
 [hast]: https://github.com/syntax-tree/hast
+
+[contribute]: https://github.com/rehypejs/rehype/blob/master/contributing.md
+
+[coc]: https://github.com/rehypejs/rehype/blob/master/code-of-conduct.md