README.md: say articles use the present format

Change-Id: Id2944b4338c0abda50996e3c885ce1bddba9ab68
Reviewed-on: https://go-review.googlesource.com/c/blog/+/190117
Reviewed-by: Jean de Klerk <deklerk@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
diff --git a/README.md b/README.md
index e0af7a3..0845e4e 100644
--- a/README.md
+++ b/README.md
@@ -19,12 +19,14 @@
 
 ## Contributing
 
+Articles are written in the [x/tools/present][present] format.
 Articles on the blog should have broad interest to the Go community, and
 are mainly written by Go contributors. We encourage you to share your
 experiences using Go on your own website, and [to share them with the Go
 community][community]. [Hugo][hugo] is a static site server written in Go that
 makes it easy to write and share your stories.
 
+[present]: https://godoc.org/golang.org/x/tools/present
 [community]: https://golang.org/help/
 [hugo]: https://gohugo.io/