feat: Implement `QuestionSkeleton` widget

[apomalyn]

As a developer, I want a generic widget to load any format of questions

Requirements

Implement a QuestionSkeleton widget that:

• takes a child
• displays
  • the instruction
  • a "Check" button at the end of the screen (and a way to override the text of the button)

What needs to be done

• Under src/practice/questions/widgets, implement a QuestionSkeleton widget, that:
  • constructor needs:
  • Widget child
  • VoidCallback? onSubmitPressed
  • bool hideSubmitButton = false
  • String? submitLabel: override the continue button label
  • IntructionTypes? instruction: instruction to display. Hidden if not provided
  • UI displays:
  • in a Column with MainAxisAlignment.spaceBetween:
    • if instruction is provided and isn't InstructionTypes.custom, display Instruction widget
    • child
    • if hideSubmitButton is false: ElevatedButton, text: submitLabel or "Check" if not provided, onPressed: onSubmitPressed

Design

Not available

Dependencies

Child of #160

Depends on:

• 167

• 179