dpad partly outside screen on landscape

[nhnb]

🐞 Describe the bug

When I open the Stendhal test web client on my phone in landscape orientation, the dpad is not fully visible.

🌍 Environment

• Web client test-version

[AntumDeluge]

It currently uses an absolute position relative to the page (defaulting to a position I chose from landscape in the Android client). Position can be adjusted in settings, but it's not convenient for players to adjust it every time they change orientation. I suppose we need figure out how to adjust positioning automatically for orientation & scaling.