People using screen readers might have a hard time knowing what a
progressbar is about unless we provide a label for it. Axe was reporting
failures like:
```
aria-progressbar-name: ARIA progressbar nodes must have an accessible
name (serious)
https://dequeuniversity.com/rules/axe/4.10/aria-progressbar-name?application=axeAPI
The following 1 node violate this rule:
Selector: .progress
HTML: <div class="progress" role="progressbar" tabindex="0"
aria-valuenow="0.0" aria-valuemin="0" aria-valuemax="100">
<div class="progress-meter" style="width: 0.0%"></div>
</div>
Fix any of the following:
- aria-label attribute does not exist or is empty
- aria-labelledby attribute does not exist, references
elements that do not exist or references elements that are empty
- Element has no title attribute
```
Note that, in the case of the ballot progressbar, it's easier to use
`aria-labelledby`, while in other place it's easier to use `aria-label`,
so we using the easier solution in each scenario.
