chore(flatpak): add systemconfig extension (#10472)

Signed-off-by: Angelo Verlain <37999241+vixalien@users.noreply.github.com>

build/flatpak/app.zen_browser.zen.yml.template

@@ -9,6 +9,9 @@ add-extensions:
     directory: lib/ffmpeg
     version: '24.08'
     add-ld-path: .
+  app.zen_browser.zen.systemconfig:
+    directory: etc/zen
+    no-autodownload: true
 command: launch-script.sh
 finish-args:
   - --allow=devel
@@ -50,6 +53,7 @@ modules:
     build-commands:
       - mv zen /app/
       - mkdir -p /app/lib/ffmpeg
+      - mkdir -p /app/etc/zen
 
       - install -Dm0755 metadata/launch-script.sh ${{FLATPAK_DEST}}/bin/launch-script.sh
       - install -Dm0644 metadata/policies.json ${{FLATPAK_DEST}}/bin/distribution/policies.json