Added dockerfile for Flatpak build

flatpak/Dockerfile

@@ -0,0 +1,15 @@
+FROM fedora:30
+
+MAINTAINER robozman "https://gitlab.com/robozman"
+
+VOLUME [ "/sys/fs/cgroup", "/tmp", "/run" ]
+
+
+RUN dnf -y update && \
+    dnf install -y flatpak flatpak-builder ostree fuse wget curl elfutils dconf git bzip2 bzr python3 python3-pip && \
+    dnf clean all
+
+RUN flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
+
+RUN flatpak install -y org.gnome.Platform//3.32 && \
+    flatpak install -y org.gnome.Sdk//3.32