[OpenJDK 2D-Dev] RFR: 8161407: Provide a javadoc description for java.desktop module

[Phil Race]

https://bugs.openjdk.java.net/browse/JDK-8161407

The top-level "api/index.html" provides for including a summary 
description of a module
taken from text in module-info.java

eg java.base has

/**
  * java.base defines and exports the core APIs of the Java SE platform.
  */

This fix adds the same kind of summary for desktop

diff --git a/src/java.desktop/share/classes/module-info.java 
b/src/java.desktop/share/classes/module-info.java
--- a/src/java.desktop/share/classes/module-info.java
+++ b/src/java.desktop/share/classes/module-info.java
@@ -23,6 +23,10 @@
   * questions.
   */

+/**
+  * java.desktop defines and exports the UI and graphics APIs of the
+  * Java SE platform.
+  */
  module java.desktop {
      requires public java.datatransfer;
      requires public java.xml;

-phil