[Feature] Adding what to connect in echarts.connect

### What problem does this feature solve?

- Right now, echarts.connect will connect every aspect of the connected figures (xaxis, yaxis, etc)
- In many cases however, you desire to only connect one aspect.
- Example in Bokeh: https://docs.bokeh.org/en/2.4.3/docs/user_guide/interaction/linking.html#linked-panning
- In the example, xaxis of all 3 figures are connected. But yaxis of only first 2 figures are connected.

### What does the proposed API look like?

Proposed API: Adding what to connect in the connect function:
``` js
echarts.connect([chart1, chart2, chart3], 'xAxis');
echarts.connect([chart1, chart2], 'yAxis');
```