::before pseudo element with display:block stops balancing

**Original Title**: ::before pseudo element used as accent stops balancing.

### Expected Behaviour
I'd like to use graphical accents for a number of headlines. If I add these using a ::before pseudo-element, I'd like the text to continue to balance.

### Actual Behaviour
When I include a ::before pseudo-element as an accent, the text is not balanced.

### Reproduce Scenario (including but not limited to)

#### Steps to Reproduce

#### Platform and Version
3.3.0 / Testing on Chrome (Mac OS)

#### Sample Code that illustrates the problem
```
h2::before {
content: "";
display: block;
background: url("images/graphic-wave.png");
background-size: contain;
width: 100px;
height: 26px;
margin-bottom: 32px;
}

balanceText('h2', {watch: true});
```

#### Logs taken while reproducing problem

Start with the balanceText('h2', {watch: true}) call and reproduce the issue in Chrome using the provided h2::before example with display:block. Trace how the plugin measures and balances the heading when the pseudo-element is present. Done means headlines with this accent continue to balance correctly without breaking the existing behavior.

Written by the indexing model from the issue text.