Add auto-hear preference

[catherinecarter]

Similar to Number Play and Number Compare, the speech button has an "auto-hear" feature to allow the user to hear the phrase association with the number bond.

The phrase will be read aloud in the language chosen (of course, provided the user has the language in their operating system) when:

• For Intro, Ten, and Twenty screens:
  • the user visits a new scene
  • the user changes addends by moving an objects between the left and right locations, or by changing the color of an object.
• For the Sum screen:
  • the user adds or removes an object from the counting area

If a user takes an action before the phrase has completed, the phrase will cut itself off and start again, finishing only if/when the user does not take any action before the phrase has time to finish.

In the preferences menu, the option title would be: "Automatically Hear Phrase" and the subtext would be, "Hear the phrase updated automatically as you interact."