Selector for responsive containers in navbar

The `[class ^="container"]` selector doesn't work in some cases. e.g.

```html
<div class="navbar">
  <div class="py-2 container">...</div>
</div>
```

And it has a potential to break user's custom CSS:

```html
<div class="navbar">
  <div class="container-custom">...</div>
</div>
```

Even with some increase CSS, should not use attribute selectors for safety.