Add a message about the mobile support

[orhun]

Currently we show a random message on mobile about CMF is not being supported. However, if you click the button you can still use the player. The problem is, the playback is sometimes jittery and glitchy on mobile.

But still, mods do work a significant number of times. Maybe we should show a warning in header/footer about this and make it more apparent that CMF is still usable on mobile.

Another idea is adding a "tap me to proceed to the player" sort of mini-text.

Ideas and feedback are welcome!

[orhun]

We just merged #48 (highly appreciated) but we still need to work a bit on this.