Specifies index bar titles for a section element.
Index titles only appear when the user activates fast scrolling.
Values for indexTitles
The indices displayed on the index bar. Each index pair is a space-separated value. For example,
indexcreates an index bar with three entries,
Titles=”0 A 109 D 198 G”
G, which fast scrolls the focuses to indexes 0, 109, and 198, respectively.