Project: chart
Task (challenging): -In `./common/ScatterChart.js`, class `ScatterChart` inherits from `LineChart`, `ScatterChart`:
  - options.pointStyle is default circle
  - options.dataLabels is always true
  - all `.dataset` lines are hidden
- Select the option `Scatter Chart` of `#type` to create `ScatterChart` instance, and make `#dataLabels` disabled