Add Contribute section to readme.md

readme.md

@@ -75,6 +75,13 @@ instead of natural language.  This hides mentions from [`retext-spell`][spell],
 *   [`retext-equality`][equality]
     — Check possible insensitive, inconsiderate language
 
+## Contribute
+
+See [`contribute.md` in `retextjs/retext`][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]
@@ -106,3 +113,7 @@ instead of natural language.  This hides mentions from [`retext-spell`][spell],
 [equality]: https://github.com/retextjs/retext-equality
 
 [syntax-urls]: https://github.com/retextjs/retext-syntax-urls
+
+[contribute]: https://github.com/retextjs/retext/blob/master/contributing.md
+
+[coc]: https://github.com/retextjs/retext/blob/master/code-of-conduct.md