[gtk/matthiasc/for-master] Mention nightly flatpaks in the README

[Matthias Clasen <matthiasc src gnome org>]

commit 8909ad18596a34b4e679dbc8c5fdb5d958284d6a
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Apr 24 11:41:44 2021 -0400

    Mention nightly flatpaks in the README

 README.md | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/README.md b/README.md
index e0b8b40c07..04f8c399b8 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,13 @@ Nightly documentation can be found at
   - Gdk: https://gnome.pages.gitlab.gnome.org/gtk/gdk4/
   - Gsk: https://gnome.pages.gitlab.gnome.org/gtk/gsk4/
 
+Nightly flatpaks of our demos can be installed from the
+[GNOME Nightly](https://wiki.gnome.org/Apps/Nightly) repository:
+  - flatpak remote-add --if-not-exists gnome-nightly https://nightly.gnome.org/gnome-nightly.flatpakrepo 
+  - flatpak install gnome-nightly org.gtk.Demo4
+  - flatpak install gnome-nightly org.gtk.WidgetFactory4
+  - flatpak install gnome-nightly org.gtk.IconBrowser4
+
 Building and installing
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