[Feature Request] Need horizontal virtual scroll for table have big columns

### 选择要提交 issue 的库
vue-easytable

### Issue 类型
Feature

### Issue 标题
Need horizontal virtual scroll for table have big columns

### 这个功能解决了什么问题？
I have a table with > 1M columns. Pagination can resolve big rows, but not working with big columns

### 你期望的 API 是什么样的？
Table have horizontal virtual scroll