Support adaptive-icons

[Findus23]

When viewing an app with an adaptive icon, fdroid tries to read /fdroid/icons-480/com.Slack.20009410.png.

But this is not a png, but rather an binary xml file.

$ cat com.Slack.20009410.png && echo "\n"
��4
adaptive-iconandroid

background

foreground**http://schemas.android.com/apk/res/android�
▒��������▒��������▒����\n                             �▒����$��������8������������

$ cat com.Slack.20009410.png| base64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==