qmlformat removes single blank lines which were useful for grouping related properties

Here is the QML code before qmlformat edited it:

```

QtObject {
property color primaryDark: '#802566'
property color primaryMediumDark: '#a72a74'
property color primaryMedium: '#d42e83'
property color primaryMediumLight: '#e86cb0'
property color primaryLight: '#f1bfdd'

property color secondaryDark: '#511d6f'
property color secondaryMediumDark: '#7b2a88'
property color secondaryMedium: '#983597'
property color secondaryMediumLight: '#cd95cb'
property color secondaryLight: '#e0bfdf'

property color neutralDark: '#262527'
property color neutralMediumDark: '#5a575c'
property color neutralMedium: '#827e85'
property color neutralMediumLight: '#a6a3a8'
property color neutralLight: '#f2f2f3'

```

And here is how it looked afterward:

```
QtObject {
property color primaryDark: "#802566"
property color primaryMediumDark: "#a72a74"
property color primaryMedium: "#d42e83"
property color primaryMediumLight: "#e86cb0"
property color primaryLight: "#f1bfdd"
property color secondaryDark: "#511d6f"
property color secondaryMediumDark: "#7b2a88"
property color secondaryMedium: "#983597"
property color secondaryMediumLight: "#cd95cb"
property color secondaryLight: "#e0bfdf"
property color neutralDark: "#262527"
property color neutralMediumDark: "#5a575c"
property color neutralMedium: "#827e85"
property color neutralMediumLight: "#a6a3a8"
property color neutralLight: "#f2f2f3"
```

I would prefer to keep the single blank lines that grouped those three groups of properties according to whether the property was prefixed by "primary", "secondary", or "neutral".