Added plugin to copy code with a single click

Change-Id: I1e2e8ac19770f9e24208336c5cd0cfb4b2775cb7
diff --git a/book.json b/book.json
index 2f0702d..f832c23 100644
--- a/book.json
+++ b/book.json
@@ -17,7 +17,8 @@
     "custom-favicon",
     "page-toc",
     "versions-select",
-    "ga"
+    "ga",
+    "copy-code-button"
   ],
 "pluginsConfig": {
     "favicon": "images/cord.ico",