Pitch.html example not working on firefox, but I found a soultion :)

[bertoncelj1]

Hi! Love the library.

I just noticed that the pitch.html example doesnt work in firefox and I found out why.

The problem is that canvas is put over the audi controls so they are impossible to click. A simple fix would be to add to z-index to canvas css like that:

        canvas {
            position: absolute;
            top: 0;
            z-index: -1;
        }

[qiuxiang]

thx!