[librest/gwagner/flatpak-demo-build] demo: add flatpak build to gitlab ci

[Günther Wagner <gwagner src gnome org>]

commit 706fb7829aac9a4361c521d86d23860f2810778d
Author: Günther Wagner <info gunibert de>
Date:   Tue Feb 1 23:16:08 2022 +0100

    demo: add flatpak build to gitlab ci

 .gitlab-ci.yml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 847253a..a656e19 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,3 +1,12 @@
+include:
+  - project: 'gnome/citemplates'
+    file: 'flatpak/flatpak_ci_initiative.yml'
+
+variables:
+  MANIFEST_PATH: 'examples/demo/org.gnome.RestDemo.json'
+  FLATPAK_MODULE: 'librest-demo'
+  FLATPAK_BUILD_DIR: build
+
 image: fedora:34
 
 stages:
@@ -28,6 +37,15 @@ build-librest:
       - "_build/meson-logs"
       - "_build/${CI_JOB_NAME}-report.xml"
 
+build-flatpak:
+  extends: '.flatpak'
+  stage: build
+  before_script: []
+  variables:
+    RUNTIME_REPO: 'https://nightly.gnome.org/gnome-nightly.flatpakrepo'
+    APP_ID: 'org.gnome.RestDemo'
+    BUNDLE: 'org.gnome.RestDemo.flatpak'
+
 .gidocgen-build:
   image: fedora:latest
   before_script: