Add Contribute section to readme.md

readme.md

@@ -53,6 +53,13 @@ Pass a [vfile][], list of vfiles, or a list of messages
 *   `nonfatal`: warning or info messages
 *   `total`: all messages
 
+## Contribute
+
+See [`contribute.md` in `vfile/vfile`][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]
@@ -74,3 +81,7 @@ Pass a [vfile][], list of vfiles, or a list of messages
 [author]: http://wooorm.com
 
 [vfile]: https://github.com/vfile/vfile
+
+[contribute]: https://github.com/vfile/vfile/blob/master/contributing.md
+
+[coc]: https://github.com/vfile/vfile/blob/master/code-of-conduct.md