Link documentation to "Specifying environment variables for actions" design doc.

Fix #2730

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PiperOrigin-RevId: 151116555
MOS_MIGRATED_REVID=151116555

site/designs/_posts/2016-06-21-environment.md

diff --git a/site/designs/_posts/2016-06-21-environment.md b/site/designs/_posts/2016-06-21-environment.md
index 5f57177..9a45f2a 100644
--- a/site/designs/_posts/2016-06-21-environment.md
+++ b/site/designs/_posts/2016-06-21-environment.md
@@ -5,7 +5,7 @@
 
 # Specifying environment variables for actions
 
-**Status**: Implemented.
+**Status**: Implemented. See [documentation](/docs/skylark/lib/ctx.html#action)
 
 **Author**: [Klaus Aehlig](mailto:aehlig@google.com)