add zoom_use_ctrl_key editor option

[eviltik]

editor.zoom_use_ctrl_key = false will remove the need of pressing Ctrl Key for zooming.

[jerosoler]

Hello,

Thanks for the PR.

I study the case. Since currently no key can be set.

Also this can be done in a simple way, adding before the start function.

    editor.zoom_enter = function(event, delta) {
        event.preventDefault()
        if(event.deltaY > 0) {
            // Zoom Out
            this.zoom_out();
        } else {
            // Zoom In
            this.zoom_in();
        }
    }