ENYO-1126: Accessibility: Add "readAlert()" to enyo
ENYO-1126: Accessibility: Add "readAlert()" to enyo

The readAlert API is for calling tts api of system service. Most of
cases accessibility supports focus based readout, but ux scenario
sometimes wants application reads a message dynamically. We provides the
readAlert API to cover it.

https://jira2.lgsvl.com/browse/ENYO-1126
Enyo-DCO-1.1-Signed-off-by: Jaewon Jang <jaewon98.jang@lgepartner.com>

enyojs/enyo,enyojs/enyo,PKRoma/enyo,PKRoma/enyo