Add new Android Security Overview to AOSP Website

Change-Id: I0fa598d926903d919db6a2c8de464bf18dafa465
diff --git a/src/tech/sidebar.md b/src/tech/sidebar.md
index b770eb8..4d8a6e7 100644
--- a/src/tech/sidebar.md
+++ b/src/tech/sidebar.md
@@ -1,3 +1,4 @@
 # Topics #
 - [Dalvik](/tech/dalvik/index.html)
 - [Encryption](/tech/encryption/index.html)
+- [Security](/tech/security/index.html)