Final cleanup

[Zetouny]

Alright guys, this is it.
I hope that this could be the last PR for this project.

• Major changes to questionPage.js
  • questionPage.js functions moved to a new seperate file.
  • Unified all the DOM selectors to use querySelector instead of getElementById.
  • Removed/Adjusted a couple of lines that were either duplicated or not necessary.
• Added Mute/Unmute Button
• Minor adjustments to Mobile Design

I learned something new, and I thought to share it with you guys. You will find a couple of functions in questionPage.js starts with run. For example run.nextQuestion, or run.skipQuestion. That's because I imported all the functions from the new file without declaring each one of them by using the following import statement
import * as run from './questionPageFunctions.js' //You can replace "run" with any keyword.

[MBreathe]

still not over you re-writing if statements, but the rest lgtm