Show user's avatar in quick comment

We have awesome quick reply feature introduced in %9.2

It looks like that:

As you can see, user's avatar is not shown while ajax's processing.
But we already have user's avatar loaded on the page in the header:

The original avatar's size is loaded. In the header we just set the size to 26:

<img width="26" height="26" class="header-user-avatar" src="https://gitlab.com/uploads/user/avatar/86853/avatar.png" alt="Avatar">

So, if we have avatar already loaded on the page, why not to show it in the quick comment (with gray effect)? 🙂

/cc @tauriedavis @kushalpandya