Add box64 to run x86_64-only programs on AArch64

Dropbox publishes its Linux client for x86_64 only. box64 lets the aarch64
dropbox package run that client, and it has to be published before dropbox
can build for aarch64.

Pinned past v0.4.5-1 because that release crashes in its glib wrapper when
Dropbox starts its tray icon. It ships without a binfmt handler so it does
not compete with qemu-user-static-binfmt.

pkgbuilds/box64/.omarchy/package.json

@@ -0,0 +1,4 @@
+{
+  "source": "local",
+  "release_ring": "fast"
+}