[lib] Added overview of script run class

Author: mta452

tehreer-android/src/main/java/com/mta/tehreer/unicode/ScriptRun.java

@@ -16,6 +16,9 @@
 
 package com.mta.tehreer.unicode;
 
+/**
+ * A <code>ScriptRun</code> object represents a sequence of characters which have the same script.
+ */
 public class ScriptRun {
     /**
      * The index to the first character of this run in source text.