Move app install scripts to /usr/bin

overlay/usr/bin/install_protonup.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+echo "**** Installing/upgrading ProtonUp-Qt via flatpak ****"
+
+# Install ProtonUp-Qt
+flatpak --user remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo 
+flatpak --user install --assumeyes --or-update net.davidotek.pupgui2
+
+# Configure Firefox as the default browser
+echo "Configure ProtonUp-Qt..."
+sed -i 's/^Categories=.*$/Categories=Utility;/' \
+    ${USER_HOME}/.local/share/flatpak/exports/share/applications/net.davidotek.pupgui2.desktop
+
+echo "DONE"