Hash vars incorrectly highlighted in doube-quoted strings

Hash variables are being incorrectly highlighted when in double quoted strings.
They are displayed as a regular text...

Eg. (in puppet resource attributes): 
```puppet
path    => "/path/${files['some']}",
```

As well as resource titles:
```puppet
    file { "/path/${config['file']}":
        ensure    => present,
    }
```

Plugin version: 0.23.0