Import the default font when loading an office document

[Cuperino]

Is your feature request related to a problem or a limitation? Please describe...
Different software has different default fonts they use as fallback. This makes it so QPrompt's default font often fails to match the font from imported text documents.

Describe the solution you'd prefer
We should be able to detect the default font from the document's metadata and set that to be the default font early in the filtering process.

This process however would only work for imported documents, not for text pasted from those same formats, as text being copy-pasted lacks that information in its metadata.