Add a simple font viewer

Currently helloSystem does not know what to do with font files.

Thought this was a good use case for pure Qml:

```
#!/usr/bin/env qml

import QtQuick 2.15

Item {
width: 480; height: 300

FontLoader {
id: loadedFont; source: Qt.application.arguments[2]
}

Text {
text: "Hamburgefonstiv"
font.family: loadedFont.font.family
font.weight: loadedFont.font.weight
font.pixelSize: 48
}
}
```

But:

```
FreeBSD% Desktop/fontviewer.qml /usr/local/share/fonts/SourceCodePro/SourceCodePro-Black.ttf
file:///usr/home/user/Desktop/fontviewer.qml:15: TypeError: Cannot read property 'weight' of undefined
file:///usr/home/user/Desktop/fontviewer.qml:14: TypeError: Cannot read property 'family' of undefined
file:///usr/home/user/Desktop/fontviewer.qml:15: TypeError: Cannot read property 'weight' of undefined
file:///usr/home/user/Desktop/fontviewer.qml:14: TypeError: Cannot read property 'family' of undefined
QQmlApplicationEngine failed to load component
file:///usr/local/share/fonts/SourceCodePro/SourceCodePro-Black.ttf:1:1: Expected token `numeric literal'
```

__Why `Expected token 'numeric literal'`?__ How to fix?