updating all hbs and js file code examples to get ribbon implementation working

[mansona]

ember-learn/guides-app#7

This is now ready and constitutes a "good enough" approach for how we tackle this for now. I have manually reviewed all code examples in the 2.17 release and I'm happy that it is doing something sensible for all/most cases 👍

[locks]

👌

[mansona]

btw my "manual" review was using this snippet in the chrome console 😍

function scrollToNext(index) {
  let block = document.getElementsByTagName('pre')[index];
  if(block) {
    block.scrollIntoView();

    setTimeout(() => {
      scrollToNext(index+1);
    }, 1000)
  } else {
    document.getElementsByClassName('next-guide')[0].click();
    setTimeout(() => {
      scrollToNext(0);
    }, 100)
  }
}

scrollToNext(0)

[jenweber]

Reviewed in staging.