content: Add link to Czech translation

Change-Id: Id1770945cd722be4b3ba38c986176f08291652cb
GitHub-Last-Rev: 67d48d1827d68d1d0ad7fb73fcffd64a3bd9a96d
GitHub-Pull-Request: golang/tour#572
Reviewed-on: https://go-review.googlesource.com/126335
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
diff --git a/content/welcome.article b/content/welcome.article
index 856f9fa..791b73c 100644
--- a/content/welcome.article
+++ b/content/welcome.article
@@ -51,6 +51,7 @@
 - [[https://go-tour-ca.appspot.com/][Catalan — Català]]
 - [[https://tour.go-zh.org/][Simplified Chinese — 中文(简体)]]
 - [[https://go-tour-zh-tw.appspot.com/][Traditional Chinese — 中文(繁體)]]
+- [[https://go-tour-cz.appspot.com/][Czech — Česky]]
 - [[https://go-tour-fr.appspot.com/][French — Français]]
 - [[https://go-tour-de.appspot.com/][German — Deutsch]]
 - [[https://go-tour-he.appspot.com/][Hebrew — עִבְרִית]]