ECharts support in markdown documentation

Recent release of znai adds ECharts native support.

Multi-column CSV file as input — beautiful charts as output

Use markdown fence block

```linechart {legend: true}
day, RPG, RTS, FPS
Monday, 100, 10, 0
Tuesday, 50, 50, 20
Wednesday, 10, 30, 50
Thursday, 5, 5, 100
Friday, 0, 100, 10
```

Or znai markdown extension

:include-linechart: charts/daily-genres.csv {legend: true}

Automatic support for dark and light theme.

And out of the box presentation mode reveals a portion of a chart at a time.

Head over to GitHub to star and learn more: https://github.com/testingisdocumenting/znai