feat:Infowindow support horizontalAlignment verticalAlignment

[deyihu]

fix #2812

  point.setInfoWindow({
            content: '<div class="info"><h1>hello</h1></div>',
            title: 'world',
            // custom: true,
            verticalAlignment: 'middle',
            // dx: 100
            horizontalAlignment: 'middle'
        })