Add unit

Add unit in both Y axis and tooltip display

Apache ECharts offer the availability to add a unit formatter.

There are two functions to provide. One for Y axis and one for the tooltip:

            yAxis: {
              axisLabel: {
                formatter: "{value} °C"
              }
            },
            tooltip: {
              valueFormatter: (value, _dataIndex) => Math.round(value * 100) / 100 + " °C",
            },
          

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