epm play: Added flatpak support

prescription.d/flatpak.sh

+#!/bin/sh
+
+[ "$1" != "--run" ] && echo "Add flatpak support to system" && exit
+
+. $(dirname $0)/common.sh
+
+assure_root
+
+[ "$(epm print info -s)" = "alt" ] || fatal "Only ALTLinux is supported"
+
+# Мсправляет ошибку "enabling unprivileged user namespaces" без перезагрузки
+a= sysctl -w kernel.unprivileged_userns_clone=1
+
+epm install flatpak flatpak-repo-flathub sysctl-conf-userns
+
+if epm installed plasma5-discover ; then
+    epm install plasma5-discover-flatpak
+fi
+
+echo "Flatpak successfully installed, but epm play is the preferred way to install the software."