Allow drag and drop from outside.

[marcelo-rebello]

We currently cannot drag and drop an item from outside the grid. The reason for this is that the dragEvent method is not public. (see https://github.com/melrose13-69/vue3-dragable-grid-layout/issues/5)

The fix is easy. just have to add this bit of code anywhere in the setup of 'GridLayoutVue`

defineExpose({ dragEvent })

a nice place to add this bit is https://github.com/melrose13-69/vue3-dragable-grid-layout/blob/13711c87691cbc5c9b793f1bab90ab857e79a158/packages/vue3-drr-grid-layout/src/components/GridLayout/GridLayout.vue#L472

[donkeylmx]

i also meet this problem ，please expose ”dragEvent“ to GridLayout Ref

[web-zhangbo]

mark, please call me when issues closed, thk