[gnome-tour/bilelmoussaoui/video] document the video feature

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 8eee9c19d1565ad72d369ea90e3a8924b0dafd1f
Author: Bilal Elmoussaoui <bil elmoussaoui gmail com>
Date:   Tue Aug 18 17:52:59 2020 +0200

    document the video feature

 README.md | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
---
diff --git a/README.md b/README.md
index d031d46..b464976 100644
--- a/README.md
+++ b/README.md
@@ -2,5 +2,23 @@
 
 
 
+### Video Feature
+Tour uses by default the logo of the distribution based on the info from `/etc/os-release`. The application 
comes with a feature to replace the logo with a welcome video shipped by the distribution.
 
+To enable the feature, you need to build the application with
+```bash
+meson _builddir -Dvideo_path=/absolute/path/to/the/video.mp4
+```
 
+If you're testing the application using Builder, make sure to change the `config-opts` accordinagly & give 
the application filesystem access so it can play the video file.
+
+Example:
+
+This needs to be added to the `gnome-tour` module
+```json
+"config-opts" : [
+    "-Dvideo_path=/home/username/to/the/video.mp4"
+]
+```
+
+along with `--filesystem=home` in `finish-args`