Link to one templating system as an example.

On issue 1887, I said that we try to steer people to templating systems, but that's kind of a weak claim at present.

google#1887
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=79954411

Author: cpovirk

guava/src/com/google/common/html/HtmlEscapers.java

@@ -26,6 +26,9 @@
  * attribute values and <em>most</em> elements' text contents. When possible,
  * avoid manual escaping by using templating systems and high-level APIs that
  * provide autoescaping.
+ * One Google-authored templating system available for external use is <a
+ * href="https://developers.google.com/closure/templates/">Closure
+ * Templates</a>.
  *
  * <p>HTML escaping is particularly tricky: For example, <a
  * href="http://goo.gl/5TgZb">some elements' text contents must not be HTML