[Glitch] Fix pop-out player appearing on mobile screens in web UI

Port 18ca4e0e9a to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/actions/app.js

@@ -0,0 +1,6 @@
+export const APP_LAYOUT_CHANGE = 'APP_LAYOUT_CHANGE';
+
+export const changeLayout = layout => ({
+  type: APP_LAYOUT_CHANGE,
+  layout,
+});