Added focus_choice_button_node function to Choices subsystem

[DJLink]

Recently added this function to my own code base for something, thought it could be useful for OG codebase, the possibility of setting a different choice focus later after showing the question.

User could set this for example to be called after choices are shown by getting the signal question_shown.

Dialogic.Choices.focus_choice_button_node(button_index);

[Jowan-Spooner]

Hi @DJLink, this looks pretty good. I thought I had added a similar helper method for selectting/pressing/activating the focused choice before but now I can't find it.
I would consider shortening those method names (the addition of button_node seems a bit over-kill).

• focus_choice()
• get_choice_button()
• select_choice()
• select_focused_choice()
  the last two don't exist, but I think would make sense, so feel free to add them if you want.

Also no ; at the end of lines please.

[DJLink]

hello @Jowan-Spooner thanks for checking, as suggested I renamed it to select_focused_choice.
removed that ; (habits from other languages, sorry xD)