added the ability to hide the help button (basically just for the finish screen, because it has a bigger discord button in the same place)
holding shift while opening the setup wizard now opens it in passive mode, aka it will install only what you need. this is mostly for testing and likely will be nuked before this code as a whole is made part of the official emulator, but it might not
additionally, the CreateHelpContent method is now no longer locked to returning an Avalonia `Control`.
the WithHelpContent method also has logic to handle it returning a string directly, and will wrap it in a textblock with h1 style and size 20 font. otherwise it's up to the ContentPresenter for the help content to choose how to display it if it's none of the above mentioned types.
