0.3.2 - Android ROM import

A fix for choosing a ROM on Android, reported in
issue #2: Browse
opened the file picker, but selecting a valid ROM came back with
"cannot open ROM".

Android returns a content:// document URI from its file picker. The setup
screen was treating that as an ordinary filename, so it failed before it
could check the ROM. It now reads the document through SDL, stages it inside
the app's folder, and passes it through the existing ROM checks and installer.
Failed reads, invalid images and files larger than 8 MiB leave an existing
installation alone, and the temporary import file is removed afterwards.

The original failure and the fix were both checked on an AYANEO Pocket S2
Pro. Browse now installs the ROM and reaches the main menu, the installed
copy has the expected SHA-1, and restarting still works after the original
selected file is removed. Selecting an already installed ROM on Windows
also remains supported.

The Android download keeps the same signing certificate as 0.3.1 and includes
both arm64-v8a and x86_64. Its version code is now 5, so it can be installed
over the previous release. As before, it is debug-signed.

Everything else is as in
0.3.1,
including what these downloads contain and the ROM you still have to supply
yourself. No ROM or game assets are included.