update: find PNG when recommended icon is an XML file

APKs can now use XML files for vector graphics like the app icon. `aapt`
returns the XML file by default, and perhaps also androguard.  This
checks if the icon is an XML file, and if so, it tries to find a PNG in
the APK with the same name and density to use instead

closes #322

This should also ultimately make the XML file available as an icon source
as well fdroidclient#1091
parent c14cbeb0
Pipeline #9626397 passed with stage
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