Unable to create DMG using path with space in app name

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Environment:
```
NPM: 10.8.1
APPDMG: 0.6.6
OS: macOS 13.5.2
```

My config.json is setup as the following:
```
{
"title": "My App",
"icon": "./icon.icns",
"background": "./bacground.png",
"icon-size" : 94,
"contents": [
{
"x": 408,
"y": 212,
"type": "link",
"path": "/Applications"
},
{
"x": 200,
"y": 212,
"type": "file",
"path": "My App.app"
}
]
}
```

These paths do not work,
`"path": "My App.app"`
`"path": "My\\ App.app"`

The console shows an error,
```
[15/21] Copying files... [FAIL]
Error: Command failed: cp -R .../My App.app
```

However, when creating a DMG with the same config without a space in the app file path,
`"path": "MyApp.app"`

This is able to successfully build a DMG.

Reproduce the failure using the provided config.json and an app named “My App.app”. Start by tracing the code behind the “[15/21] Copying files...” step and compare it with the working “MyApp.app” case. Done means a DMG builds successfully when the app path contains a space.

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