Hopefully fix Windows icon background color

See https://learn.microsoft.com/en-us/windows/msix/desktop/desktop-to-uwp-manual-conversion#optional-add-target-based-unplated-assets

.ci/windows/build.bat

@@ -39,6 +39,7 @@ windeployqt --qmldir resources\qml\ NhekoRelease\nheko.exe
 mkdir msix
 xcopy .\NhekoRelease\*.* msix\*.* /s /e /c /y
 copy .\resources\nheko.png msix
+copy .\resources\nheko.png msix\nheko_altform-unplated.png
 copy .\resources\AppxManifest.xml msix
 del msix\vc_redist*
 ::sed -i "s/ Version=[^ ]*/ Version=\"%WINVERSION%\"/" msix\AppxManifest.xml