feat: Added Torzu's AppImageBuilder

Added support for building AppImages using Torzu's AppImageBuilder.

Signed-off-by: Boss.sfc <boss.sfc@citron-emu.org>

AppImageBuilder/assets/AppRun

@@ -0,0 +1,11 @@
+#! /bin/bash
+
+cd "$APPDIR"
+
+if [ -d /usr/lib/$(uname -m)-linux-gnu/qt5 ] || [ -d /usr/lib/qt ]; then
+    # System-wide Qt5
+    exec ./citron.sh "$@"
+else
+    # Bundled Qt5
+    exec ./citron-bqt.sh "$@"
+fi