Project: svg-chart
Task (easy): In `common/LineChart.js`:
- append g element (class `datasets`) inside `svg` and make it fill the entire `svg` (no padding between them)
- append a polyline (class `dataset dataset-${index}`) inside `.datasets` for each `config.data.datasets` item (AKA. `dataset`)
- all lines have unique colors
- The min and max axis-y values correspond to the min and max values of all `dataset.data`