mixed touch/mouse devices not supported

[niklasf]

This is tricky, but some devices can be used with a mouse but have a touch screen.

Examples:

• window.lichess.mousedownEvent
• https://github.com/ornicar/chessground/commit/04c68e18444754890b322313c17db1619da0ac87

[abeswick]

do you know which browser it should work in on the ipad? I'm sure it is the browser that is the problem but i can try

[niklasf]

Only remaining issue: #5631