Can't set a custom icon on iPad

[chucks]

When you attempt to set a custom icon from Settings…Appearance on iPad, the first tap on a custom icon will select it, but nothing else will happen. If you tap again, you'll see a confirmation from the system, but the stock icon will be in the dialog box, and the actual icon on device will not be changed.

Exported.mov

When the app attempts to set the custom icon, it fails with an error, which is suppressed by a fire and forget effect

Error Domain=NSCocoaErrorDomain Code=4 "The file doesn’t exist." UserInfo={_LSLine=191, NSUnderlyingError=0x6000031a8210 {Error Domain=LSApplicationWorkspaceErrorDomain Code=-105 "iconName not found in CFBundleAlternateIcons entry" UserInfo={_LSLine=179, NSLocalizedDescription=iconName not found in CFBundleAlternateIcons entry, _LSFunction=-[LSAltIconManager _setAlternateIconName:forIdentifier:withIconsDictionary:error:]}}, _LSFunction=-[LSAltIconManager _setAlternateIconName:forIdentifier:withIconsDictionary:error:]}

I'll submit a PR to update info.plist to register the custom icons for iPad specifically.

[stephencelis]

Closed by #79. Thanks so much!