feat: put the retrobios app on a handheld card

--add-app, the result screen and a [y/N] question put the launcher of
muOS, KNULLI or ROCKNIX on the card the BIOS folder is on. The files come
from install/launchers/index.json at the same ref, each checked by size
and SHA-256 before the first is written, and the app event reports it.

install.ps1

@@ -11,7 +11,7 @@
 
     $ErrorActionPreference = "Stop"
     $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-    $defaultInstallSha256 = "be9d37048e800072d6d5d2a40afaa5a46d5b062577f83c0fa633fc15159de66a"
+    $defaultInstallSha256 = "cec348d9aa6c9f940a2c9dc9bc6414a923acea8137e4a3624d4710c9d88c38ad"
     $maximumInstallerBytes = 2MB
     $installerExit = 0
     $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }