Add some docs about alerts

[elessar-ch]

No description provided.

[FKSI]

Hum 🤔

[elessar-ch]

Thx @FKSI for pointing out the typo

[davidknezic]

Wondering if this could also be split up into multiple snippets, so it's easier to figure out which example belongs to what code snippet. Thoughts @elessar-ch @FKSI?

[FKSI]

If split, I'd see

<div class="alert alert-success" role="alert">
  <strong>Well done!</strong> You successfully read this important alert message.
</div>
<div class="alert alert-info" role="alert">
  <strong>Heads up!</strong> This alert needs your attention, but it's not super important.
</div>
<div class="alert alert-danger" role="alert">
  <strong>Danger!</strong> Are you sure you want to release the raptors?
</div>

And

<div class="alert alert-warning alert-dismissible" role="alert">
  <strong>Warning!</strong> Pushing the x on the right will remove this alert. For EVER!
  <button type="button" class="close" data-dismiss="alert" aria-label="Close">
    <span aria-hidden="true">&times;</span>
  </button>
</div>

[davidknezic]

Agree, it would be the different appearances first and then how to make it dismissable.

[elessar-ch]

I think that tiny little bit of code should be clear enough for anybody.