Make textbox contents accessible to screen readers

[fbcideas_migusr]

Currently, when a screen reader like JAWS encounters a textbox, the contents of the textbox are not accessible. At the least, the Show Data table should produce a single-cell table containing the contents of the textbox. Ideally, the contents of the textbox would be available to the screen reader without having to go to the Show Data table.

[fbcideas_migusr]

Maybe an improvement on this idea would be to auto-populate alt text for text boxes with the text box contents by default.

[Aino_Leppanen2]

A very important feature indeed, especially if and when your visualizations require a bit of explaining.