Function: chosen

--Usage--
> chosen(choice: some_string, some_multiple_choice_value)

Is the given choice selected in the [[type:value#multiple_choice|multiple choice value]]?

--Parameters--
! Parameter	Type			Description
| @input@	[[type:string]]		Multiple choice value to look in.
| @choice@	[[type:string]]		Choice to look for.

--Examples--
> chosen(choice: "red",  "red")        ==  true
> chosen(choice: "red",  "blue")       ==  false
> chosen(choice: "red",  "red, blue")  ==  true
> chosen(choice: "blue", "red, blue")  ==  true
