Add documentation on releasing plugin API JAR

Very straight-forward, just run the script Shawn provided.

Change-Id: Iaab46c9ce6bed2ec9ff0f51553797204d1d0d070
Signed-off-by: Brad Larson <bklarson@gmail.com>
diff --git a/Documentation/dev-release.txt b/Documentation/dev-release.txt
index f439504..83c47f3 100644
--- a/Documentation/dev-release.txt
+++ b/Documentation/dev-release.txt
@@ -114,6 +114,12 @@
 ** new war: [release-candidate], featured...
 ** old war: deprecated
 
+Plugin API JAR File
+~~~~~~~~~~~~~~~~~~~
+
+* Push JAR to commondatastorage.googleapis.com
+** Run tools/deploy_plugin_api.sh
+
 Tag
 ~~~